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SRWE M14 Routing Concepts — Transcript

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0:03[Music]
0:18hi
0:19hello there welcome to routing concepts
0:22no matter how effectively you set up
0:24your network
0:25something will always stop working
0:27correctly
0:29or even stop working completely
0:32this is a simple truth about networking
0:35so even though you already know quite a
0:38bit about routing
0:39you still need to know how your routers
0:42actually work
0:43so this knowledge is critical if you
0:46want to be able to troubleshoot your
0:48network
0:49so this module goes into detail about
0:51the functions of a router
0:53so let's get started
0:57so for the module objective at the end
1:00of this video lecture
1:01you should be able to explain how
1:03routers use information in packets
1:06to make forwarding decisions
1:09also included on this video lecture are
1:11subtopics like
1:13path determination packet forwarding
1:16basic router configuration review ip
1:19routing
1:20and the static and dynamic routing
1:26so let's begin with path determination
1:31okay so there are two basic functions of
1:34a router
1:35so before a router forwards a packet
1:37anywhere it has to determine the best
1:40path
1:40for the packet to take so this topic
1:43explains
1:44how routers make this determination
1:48so ethernet switches are used to connect
1:51end devices and other interior media
1:53devices
1:54such as other ethernet switch or
1:56switches
1:57to the same network so some connects
2:01okay multiple networks okay so like
2:04routers
2:05okay a router connects multiple networks
2:08which means
2:09that it has multiple interfaces that
2:12it's going to the different ip network
2:15so when a router receives an ip packet
2:17on one interface
2:18it determines which interface to use to
2:21forward the packet to the destination
2:23so this is known as routing okay
2:27so the interface that the router uses to
2:29forward a packet may be the final
2:31destination
2:32or it may be the network connected to
2:34another router
2:35that is used to reach the destination
2:37network so
2:38each network that the router connects to
2:42typically
2:43requires a separate interface
2:46but this may not always be the case the
2:49primary
2:50functions of a router are first to
2:53determine the best path
2:55to forward packets based on the
2:57information in its routing table
3:00and second to forward packets toward
3:03their destination
3:09okay now i have here an example
3:13okay router functions example so the
3:16router uses its ip routing table
3:19to determine which path or route to use
3:22to forward the packet
3:24so r1 and r2 use their respective ip
3:27routing table to first determine the
3:29best pass
3:30and then forward the packet so initially
3:34we have here the source okay and the
3:36destination so the source will forward
3:38the packet to the router
3:40the router will refer to the routing
3:42table if it has an entry on it
3:44and then if there is an entry it will be
3:46forwarded to the exit interface
3:48leading to another network or router
3:51in that case that is router 2. router 2
3:54will process the packet and do the same
3:56as that of router 1
3:58referring to the routing table then it
4:00will be forwarded to the destination
4:02so that's how it works okay router
4:06always refer to its routing table where
4:08to forward the packet
4:10now if there is no entry for the router
4:13okay for that packet then
4:17the router will simply drop the packet
4:20unless there is a configuration or there
4:23were configurations
4:25like the gateway of last resort
4:28where to forward the packet not found on
4:31the routing table
4:32okay all right
4:36so the next one would be the best path
4:38equal longest match
4:40so what is meant by the router must
4:43determine the best
4:44path in the routing table
4:47so the best path in the routing table is
4:49also known as the longest match
4:52so the longest match is a process the
4:54router uses to find a match
4:57between the destination ip address of
4:59the packet
5:00and a routing entry in the routing table
5:03so the routing table contains route
5:05entries consisting of
5:07a prefix or network address and prefix
5:11length so for there to be a match
5:14between the destination ip address of a
5:17packet
5:18and a route in the routing table a
5:20minimum number of far left
5:22bits must match between the ip address
5:25of the packet
5:27and the route in the routing table so
5:30the prefix length of the route
5:32in the routing table is used to
5:34determine
5:35the minimum number of far left bits that
5:38must
5:39match remember that
5:42in ib packet okay only contains the
5:45destination ip address
5:47and not the prefix length okay
5:50so the longest match is the route in the
5:53routing table
5:54that has the greatest number of far left
5:57matching bits
5:58with the destination ip address on the
6:00packet
6:02so the route with the greatest number of
6:04equivalent far left bits
6:06or the longest match is always the
6:08preferred
6:09route so take note the term prefix
6:12length
6:13will be used to refer to the network
6:15portion for both
6:17ipb4 and ipv6 ip
6:20addresses
6:25okay so ipb for address longest match
6:29example here now in the table an ipv4
6:32packet has a destination ip address or
6:35ipv4 address
6:36of 172 16
6:400.10 okay
6:43so the router has three route entries in
6:46its ipb4 routing table
6:48that matches this packet okay so this
6:51are
6:53172.16.00 12.
6:57172.16.00 that's 18
6:59and 172.16.00 it's last 26.
7:04so of the three routes 172 1600
7:09it's last 26 okay has the longest match
7:13and would be chosen to forward the
7:16packet
7:17so remember for any of these
7:20routes to be considered a match there
7:23must be at least the number of
7:25matching bits indicated by the subnet
7:29mask
7:29for the route okay so let's have an
7:33example
7:34for ipv6 okay ipv6 address longest match
7:38okay now in the table an ipv6 packet has
7:42a destination okay
7:44so 2001 colon db8
7:47colon c000 colon colon 99
7:51so this example shows three route
7:53entries but only two of them are valid
7:57match so with one of those being the
8:00longest match
8:01so the first two route entries have
8:03prefix lengths that have the required
8:05number of
8:05matching bits as indicated by the prefix
8:08link
8:09okay so the first route entry
8:14which is 2001 colon db8
8:18fall on c0 0 0 colon colon slash
8:2240 okay so the prefix length of 40
8:26matches the first or the 40 far
8:29left bits in the ipv6 address
8:33so the second one would be
8:36a prefix length of 48 so that is 2001
8:40dba c000 colon colon's last 48
8:46all right so the second route entry has
8:48a preface length of slash 48
8:51and with all 48 bits matching the
8:54destination ipv6 address
8:56and is the longest match so the third
9:00route
9:01okay which is not a match because it's
9:04last 64 prefix okay
9:08so it requires 64 matching bits
9:12so for the prefix 2001 dba c000
9:175555 colon colon 64 to be a match
9:22okay so the first 64 bits must match the
9:25destination ipv6 address
9:28of the packet so only the first
9:3148 bits match so this route entry
9:35is not considered a match okay
9:38so for the destination ipv6 packet with
9:41the address 2001
9:42dba c000
9:46holland colon slash 99 or
9:4999 slash 48 consider
9:53the following three route entries
9:56all right
10:01okay so next is build the routing table
10:06so a network a routing table consists of
10:09prefixes
10:10and their prefix lengths but how does
10:14the router learn
10:15about these networks okay
10:19so
10:24let's take a look at this topology here
10:26okay so
10:27the network okay are the presentations
10:30that i'm going to do
10:32is based on the perspective of r1
10:35now referring to the figure so the
10:38networks in the topology
10:39are highlighted and labeled from the
10:42perspective of
10:43r1 okay all ipb4 and ipv6
10:48network highlighted in yellow are
10:50directly connected
10:52so this network here 10 0 1 0
10:5624 is directly connected to r1
11:00this 10 0 2 0 slash 24 is directly
11:03connected to r1 also
11:05and so with 10 0 3 0 24
11:09so there are three subnets directly
11:12connected to r1
11:13and these are marked yellow here
11:16okay now all the ipv4 and ipv6 networks
11:20highlighted in blue are remote networks
11:23for r1
11:25okay now referring to this uh networks
11:2810 0 4 0 is last 24.
11:33you've got 2009 165
11:36200 224 slash 30. you've got 10 0 5
11:400 it's slash 24 okay
11:43and the internet is of course all of
11:46this are
11:47remote to r1 okay
11:51so there are also three networks or
11:53subnets connected to r2
11:56so these are 10 0 for 0
11:5910 0 5 0 and 209 165 200.224
12:08okay
12:10all right so different ways a router
12:14learns
12:15routes okay so basically we have several
12:18or we have three
12:19okay so the first one would be directly
12:21connected networks
12:23so directly connected networks are
12:26networks
12:26that are configured on the active
12:28interfaces of a router
12:30so a directly connected network is added
12:33to the routing table
12:35when an interface is configured with an
12:37ip address and subnet mask
12:38or prefix length and is active
12:42right so up and up on status
12:45okay so next would be the remote
12:48networks
12:49so remote networks are networks that are
12:52not directly connected to the router
12:54okay as shown in the topology presented
12:56earlier so routers
12:58learn about remote networks in two ways
13:01so first
13:02static routes so added to the routing
13:05table when a route is manually
13:07configured
13:08second is dynamic routing protocols
13:12so added to the routing table when
13:14routing protocols dynamically learn
13:16about the remote network
13:19so dynamic routing protocols include
13:21enhanced interior gateway routing
13:23protocol or
13:24eigrp open shortest path
13:27first or ospf as well as
13:30several others okay
13:34so the third one would be a default
13:37route
13:38okay a default route specifies a next
13:41hub
13:42to use when the routing table does not
13:44contain a specific route that matches
13:46the destination ip address
13:48so the default route can be entered
13:51manually
13:52a static route or learned automatically
13:55from a dynamic routing protocol
13:58so a default route over ipb4
14:02has a route entry of zero that zero the
14:060.0 or equal
14:07zero zero and a default route
14:10over ipv6 has a route entry of
14:15colon colon slash zero
14:19okay so this last zero prefix length
14:23indicates that zero bits or no bits need
14:26to be matched
14:27the destination ip address for this
14:29route entry to be used
14:32so if there is no routes with a longer
14:35mass
14:36okay so most than or more than
14:40zero bits then the default route is used
14:43to forward the packet
14:44so the default route is sometimes
14:46referred to as the gateway
14:48of last resort
14:57okay so let's talk about packet
14:59forwarding now
15:01okay so packet for warning decision
15:04process
15:05so now that the router has determined
15:07the best path
15:09okay so that is via the longest match or
15:11the best match
15:12okay so the packet based on the longest
15:16match
15:17so it must determine how to encapsulate
15:20the packet
15:20and forward it out on the correct egress
15:23interface
15:25okay so the figure here demonstrates
15:28how a router first determine the best
15:30path and then forwards the packet
15:33okay so the following steps describe the
15:36packet
15:37forwarding okay
15:40and starts or begins with the data link
15:43frame
15:43with an encapsulated ip frame or ip
15:46packet
15:47arrives at the egress or ingress
15:50interface
15:52okay so started with this one so this
15:55one here is a frame
15:57okay so you've got data link header the
15:59destination ip address
16:00the rest of the ip packet and the
16:02trailer
16:04okay so the data link frame with an
16:07encapsulated ip packet arrives on the
16:09ingress
16:10interface when i say ingress that is the
16:12incoming
16:13okay that's the input
16:17second so the router examines the
16:20destination ip address in the packet
16:22header
16:23and consult its ip routing table
16:28okay so the router finds the longest
16:31matching
16:32prefix in the routing table
16:37and then the first step would be the
16:39router encapsulates the packet in a data
16:42link frame
16:42and forwards it out the egress
16:46interface so the destination
16:49could be a device connected to the
16:51network or
16:52a next tab router okay
16:55so the fifth one would be however if
16:58there is no matching route entry
16:59the packet is dropped okay so which is
17:02the default behavior
17:04of a router
17:10so forwards the packet to a device on a
17:13directly connected
17:15network okay so if the route entry
17:19indicates that the egress interface is
17:21directly connected network
17:24this means that the destination ip
17:26address of the packet belongs to a
17:28device
17:29on the directly connected network so
17:31therefore
17:32the packet can be forwarded directly to
17:35the destination device
17:37so the destination device is typically
17:39an end device
17:40on an ethernet lan which means the
17:43packet
17:44must be encapsulated in an ethernet
17:47frame
17:49okay so to encapsulate the packet in an
17:51ethernet frame
17:52the router needs to determine the
17:54destination mac address
17:56okay associated with the ip address of
18:00that
18:00packet so the process varies
18:03based on whether the packet is an ipv4
18:06or an ipv6 okay
18:10so for the ipv4 packet the router
18:14checks each arp table for the
18:17destination ipv4 address
18:19and an associated internet mac address
18:23so if there is no match the router sends
18:26an arp request
18:28the destination device will return an
18:31arp reply
18:32with its mac address so the router can
18:35now forward the ipv4 packet
18:37in an ethernet frame with the proper
18:40destination mac address
18:43okay now in case of an ipv6 packet
18:47so the router checks its neighbor cache
18:50for the destination ipv6 address and an
18:53associated
18:55ethernet mac address so if there is no
18:58match
18:58the router sends an icmp v6
19:02neighbor solicitation or ns message
19:05the destination device will return an
19:08icmp v6
19:10neighbor advertisement or and a message
19:12with its mac address
19:14so the router can now forward the ipv6
19:17packet in an ethernet frame
19:19with the proper destination mac address
19:23okay
19:27all right so how about forwarding the
19:30packet to the next hub
19:32router so if the route entry indicates
19:36that the destination ip address is on a
19:38remote network
19:40this means that the destination ip
19:43address
19:43of the packet belongs to a device on a
19:45network
19:46that is not directly connected okay so
19:49therefore
19:51the packet must be forwarded to another
19:53router
19:54specifically a next hub router
19:58so the next hub address is indicated in
20:00the route entry
20:02so if the following router and the next
20:05hub router
20:06are on the ethernet network a similar
20:09process
20:10arp and isc icmp
20:13neighbor discovery or nd will occur
20:17for determining the destination mac
20:18address of the packet
20:21as described previously so the
20:24difference is that
20:25the router will search for the ip
20:28address of the next hub router
20:30in its arp table or neighbor cache
20:34instead of the destination ip address of
20:37the packet
20:38so take note that this process will vary
20:42for other types of player 2 networks
20:45okay so the third one would be
20:49drop the pocket so if there is no match
20:52in the routing table
20:53the default behavior of the router is to
20:55drop the packet
20:57okay so if there is no match between the
20:59destination ip address and a prefix
21:03in the routing table and if there is no
21:06default route
21:08the packet will be dropped
21:11okay so again the default behavior of
21:13the router is to drop the packet if it
21:15is not
21:16on the routing table or you have not
21:19configured
21:20okay so the default route or the gateway
21:23of last resort
21:28okay so the next one would be the
21:30end-to-end packet forwarding
21:32so the primary responsibility of the
21:35packet forwarding function
21:37is to encapsulate packets in the
21:39appropriate data link frame
21:41okay for the outgoing interface for
21:44example
21:46the data link frame format for serial
21:48could be a point to point
21:50or ppp protocol high level data link
21:53control or hdlc
21:55protocol and some other layer to
21:57protocols like frame relay
21:59or you also have atm
22:03or the old ones okay
22:09all right so i have here an example of
22:13an end-to-end packet forwarding okay
22:16so initially pc1 sends
22:19packet to pc2 okay so this is our source
22:23here
22:24and our destination is on pc2
22:27okay so in the animation
22:30ec1 sends packet to pct
22:33okay note that if an arp entry does not
22:38exist
22:39in the arp table for the default gateway
22:43192.168.1.1
22:45pc1 sends an arp request
22:48so router 1 would then reply okay
22:53with an arp reply okay
22:57so take a look at the animation here
23:00so because pc2 is on a different network
23:03i will encapsulate the packet and send
23:05it to the router
23:08all right so this package layer three
23:11data
23:13okay so that is the first half
23:16okay or the first movement of the packet
23:20now let's take a look at what will
23:22happen when the packet
23:24reaches r1 going to r2
23:28okay now r1 forwards packet
23:32to pc2
23:36okay so r1 now forwards packet to pc2
23:40because the exit interface is on an
23:43ethernet network
23:44r1 must first resolve the next hub ipv4
23:48address
23:49with the destination map address using
23:51hrp table
23:53so if an arp entry does not exist in the
23:56arp table for the nextup interface
23:58which is 192.168.2.2
24:02okay r1 sends an arp request
24:06r2 would then return an arp reply
24:10same thing with the process happened on
24:12pc1 and r1
24:15all right so it has been forwarded now
24:19to the exit interface
24:23192.168.2.1 okay
24:26now your packet now is on r2
24:29now r2 forwards the packet to r3
24:33okay r2 now forwards the packet to r3
24:37so because the exit interface is not an
24:39ethernet network
24:41r2 does not have to resolve the next up
24:43ipv4 address
24:44with the destination mac address so when
24:47the exit interface
24:49is a point-to-point serial connection
24:53the router encapsulates an ipv4 packet
24:55into a proper
24:56data link frame format used by exit
24:59interface
25:00it might be an hdlc a ppp or any other
25:04protocols
25:05so because there is no mac address on
25:07the serial interfaces
25:09r2 sets the data link destination
25:11address
25:12to an equivalent of a broadcast
25:16okay so that is from r2
25:19to r3
25:25okay next would be
25:28r3 forwards the packet to pc2 now
25:31okay so because the destination ipv4
25:34address
25:35is on directly connected ethernet
25:37network
25:38r3 must resolve the destination ipv4
25:41address of the packet
25:43with its associated mac address so if
25:46the entry is not on the arp
25:48table r3 sends an arp request
25:51out of its fast internet 0 0 interface
25:55pc2 would then return an irp reply
25:59with its mac address
26:02all right
26:07next packet forwarding mechanisms
26:10so as mentioned previously the primary
26:13responsibility of the packet forwarding
26:15function is to encapsulate packets in an
26:18appropriate data link frame
26:20okay so for the outgoing interface so
26:23the more efficiently a router
26:26can perform this task the faster packets
26:28can be forwarded by the router
26:31so router supports the following three
26:33packet forwarding mechanisms
26:35so these are brass switching
26:39fast switching and the cisco express
26:42forwarding
26:43so assume that there is a traffic flow
26:46which consists
26:47of five packets they are all going to
26:50the same destination
26:52all right okay so let's start with
26:56process switching so process switching
27:01is an older packet forwarding mechanism
27:05still available for cisco routers
27:09so when a packet arrives in the
27:10interface
27:12okay so it is forwarded to the control
27:15plane
27:16where the cpu matches the destination
27:18address
27:19with an entry in its routing table and
27:21then determines the exit
27:23interface and forwards the packet
27:26to the exit or igris interfaces
27:29now it is important to understand that
27:31the router does not
27:33or does this every packet even if the
27:36destination
27:37is on the same network
27:40for a stream of packets so the process
27:43switching mechanism is very slow and is
27:46rarely implemented in modern networks
27:49contrast this with fast switching
27:52all right now let's talk about
27:56fast switching now okay so fast
27:58switching is another
28:00older okay packet forwarding mechanism
28:03which was a successor of
28:07process switching so fast switching
28:10uses a fast switching cache to store
28:14next hub
28:15information okay so when a packet
28:19arrives on the
28:20interface it is forwarded to the control
28:23plane
28:24where the cpu searches for the match
28:27in the fast switching cache
28:31so if it is not there it is
28:34process switched and forwarded to the
28:36exit interface
28:40all right so the flow information
28:43for the packet is also stored in a fast
28:45switching cache
28:47okay
28:50if another packet going to the same
28:52destination arrives on the interface
28:54the next app information in the cache is
28:56reused without cpu intervention
28:59so with fast switching notice how
29:03only the first packet of flow is a
29:06process switched or is process switched
29:09and added to the fast switching cache
29:13so the next four packets are quickly
29:14processed based on the information
29:16of the fast switching cache
29:21all right so the last one would be the
29:24cisco express forwarding or cef
29:27ceph is the most recent and default
29:29cisco ios
29:30packet forwarding mechanism so like fast
29:34switching ceph builds a forwarding
29:37information base
29:39or fib okay
29:43and an adjacency table
29:46so however the table entries are not
29:50packed triggered like fast switching
29:53but change triggered such as
29:56when something changes in the network
29:58topology
29:59so therefore when a network has
30:02converged
30:03the fib and adjacency table contains all
30:06the information that the router would
30:08have
30:08to consider when forwarding packet
30:12so cisco express forwarding is the
30:14fastest
30:15forwarding mechanism and the default
30:18cisco routers and multi-layer switches
30:21technology
30:23so ceph builds the fib and adjacency
30:26table
30:27after the network has converged when you
30:30say converge
30:31this is the state of stability of the
30:34network
30:35okay so all five packets are quickly
30:38processed
30:39in the data plane
30:42all right
30:48okay now let's move on to the basic
30:51router configuration review
30:59okay so let's have our topology here a
31:01router creates a routing table
31:04to help it determine where to forward
31:06packets
31:08okay so but before diving into the
31:10details of the ib routing table
31:12so this topic reviews basic router
31:15configuration
31:17and verification tasks
31:20all right so the topology in the figure
31:23will be used
31:24for configuration and verification
31:26examples
31:27so it will also be used in the next
31:30topic to discuss
31:31the ip routing table so our topology
31:33comprises of
31:34several routers and switches
31:38with four clients connected to it okay
31:41so the isp or the internet is connected
31:44via r2
31:46and it might be propagated going to r1
31:50okay all right so basic configuration
31:55okay so review so to configure your
31:59router so basic setup is necessary
32:01and this basic setup includes something
32:04like configuring the hostname
32:06okay enabling the secret password via
32:09enable secret your password you've got
32:13line console 0 lagging synchronous
32:15password is called login
32:17now light console 0 is being used okay
32:21so whenever you want to get in into the
32:23router for the first time
32:24okay and prompted you a password that is
32:27the line console zero
32:29right so line vty zero to four here
32:34this is being used for remote access
32:38okay so there are five virtual lines
32:40zero to four password cisco login
32:43transport input ssh
32:45telnet exit so when you want to remotely
32:48access
32:48r1 okay so from other
32:51device or remote devices the line vty is
32:55in effect
32:56okay so this is used for remote access
32:59okay the next the next configuration
33:02here is the service password encryption
33:05okay so the service password encryption
33:08encrypted all the passwords
33:10used in the configuration all right
33:14and then you also have here the banner
33:16motd
33:18so warning and authorized access is
33:20prohibited so this will gives you
33:22some notifications okay so but then it's
33:25mostly used for legal purposes
33:27all right next
33:32for ipv6 this is how we configured ipv6
33:35of course we've started
33:37with ipv6 unicast routing and then
33:40configuring
33:41an ip address so interface gigi ethernet
33:44zero zero zero zero
33:46so description link to land one ip
33:49address
33:50ipv6 address and of course no shutdown
33:53right we have to enable the interface
33:55okay so after all the configurations
33:59we have to save it using the command
34:01copy run
34:02start all right so this is the basic
34:05configuration of a router
34:07from the basic setup to the ip
34:11assignment
34:12okay and then saving
34:16now we have some verifications or common
34:18verification commands
34:20okay so which includes show ip interface
34:22brief
34:23show run right you
34:26also have show interfaces
34:30show ip interface show ipad out and
34:33ping so in its case replace ip with ipv6
34:38if you want to use the ipv6 version of
34:40it
34:41all right
34:45okay so using our topology presented
34:48earlier
34:48okay our reference is on r1
34:51now when you have show ip interface
34:53brief it will gives
34:55us the interface name right so the ip
34:57address assigned to it
35:00so the status all right and the protocol
35:03status
35:05right if it is up or down the show ip
35:08interface
35:09brief this one is very useful in
35:10troubleshooting
35:13all right
35:17so the next one would be show ipv6
35:20interface proof
35:22now this will gives us all the ipv6
35:26configured interfaces including the ip
35:30address and the status all right
35:35next show run or show running config
35:38interface
35:39giga ethernet 000 now this would give us
35:42the details or the information about the
35:44gigabit
35:45ethernet 000 but without this option
35:49here
35:50it will show us all the configured
35:54information about the routers
35:57now in this case this gives only
35:59information about
36:01the configurations made on the specific
36:04interface which is gigabit ethernet
36:070.0 all right so the showrun command
36:11will just show us what we have
36:13configured
36:14on the device or specifically on the
36:17interface
36:20okay so if you want to get the details
36:24of the gigabit ethernet 000 or specific
36:28interface
36:29so your command should be show
36:30interfaces and then the specific
36:32interface
36:33now this would give us okay so the
36:35status
36:36all right this one is up okay
36:40line protocol is up you can also see
36:43here the
36:44ip address assigned right
36:47so the maximum transfer unit the
36:49bandwidth
36:50the delay encapsulation okay
36:54so the duplex mode and so on and that
36:57information
36:58all right relates to gigabit ethernet
37:01zero zero zero
37:06next show ip interface gigabit ethernet
37:09000
37:12right so specific information again
37:14about the interfaces
37:16okay so including the technology
37:19supported
37:20on that specific interface so something
37:23like the ipsef
37:24switching is enabled right so the mtu is
37:28still there
37:29okay the ip address
37:33and the subnet mask is also indicated
37:39next for ipv6 version of the command you
37:42can have show ipv6 interface
37:44gigabit ethernet zero zero so this is
37:46the same without of ipv4
37:50all right so the next one would be show
37:52iprout
37:54okay so this is the routing table so
37:56basically what you see here are just c
37:58and l okay so c means
38:01directly connected and l basically these
38:04are the local ip address
38:07okay or the ip address connected to the
38:09specific interface
38:10denoted by l
38:14okay now displaying the ipv6
38:17route show ipv6 route displays only
38:20the ipv6 equivalents
38:26okay and the last verification command
38:29is of course ping
38:31right so would it be ipv4 or ipv6 we
38:34have a simple command and single command
38:36ping ip address
38:41okay so we can also filter the command
38:44output
38:45okay so another useful feature
38:49that improves user experience in the
38:51command line interface or cli
38:54is filtering the show output so
38:57filtering commands
38:58can be used to display specific sections
39:00of the output
39:02so to enable the filtering command we
39:04are using the pipe
39:05character no after the show command
39:09and then enter a filtering parameters
39:12and filtering expression
39:14so this includes section
39:17include exclude and begin
39:20okay now section this displays the
39:24intersection
39:25that starts with a filtering expression
39:28okay so i'm going to give you an example
39:31as we progresses on this
39:32video lecture now include
39:36this includes all output lines that
39:39matches the filtering expression
39:42exclude this excludes all
39:45output lines that match the filtering
39:48expression
39:49so this is the opposite of include and
39:51you also
39:52begin this displays all the output lines
39:56from a certain point
39:57starting with the line that matches the
39:59filtering expression
40:02so take note that output filters can be
40:04used in combinations with
40:06show commands all right
40:10so we have here an example okay
40:14so show running config
40:17okay so pipeline section line pty so if
40:20you will observe
40:21the output should start with line vty so
40:24if you have
40:24several line vty there that would be
40:27displayed
40:28starting on that point line vty
40:31okay so instead of typing show run
40:34that will display all all the
40:36configurations made on the device
40:38or onto the router so we could simplify
40:41okay and minimize the output by using
40:44this
40:45pipeline commands all right so another
40:48example is
40:49show ipv6 interface brief
40:53include app so this will display only
40:56all configurations okay
41:00or all the status of the interface on
41:03ipv6
41:05which includes the status up
41:10all right so next would be show ip
41:13interface brief
41:15exclude unassigned okay so this will not
41:18display
41:20any interfaces that are unassigned so if
41:23you want to see only
41:26interfaces without the unassigned status
41:29or ip address there
41:30which is set to unassigned okay in the
41:33specific interface then you could use
41:35the exclude
41:36anything that you don't want to see on
41:37the output use exclude
41:43all right so next show ip route
41:46begin gateway okay
41:49so what will happen is on the routing
41:52table
41:52this is take note show ipad
41:56so this will display the routing table
41:59starting with or beginning with the
42:01gateway
42:02keyword so gateway of last resort is not
42:04set so
42:05that would give you the output
42:13all right now let's talk about ip
42:16routing table
42:20do you know how to read routing table
42:22let's see
42:23okay so let's start with route sources
42:27how does a router know where it can send
42:30packets it creates a routing table
42:33that is based on the network in which it
42:36is located
42:37so a routing table contains a list of
42:40routes
42:41to known network so prefix
42:44prefix length okay so the source of this
42:47information is derived from the
42:49following
42:50so again we've covered already directly
42:53connected networks
42:54static routes dynamic routing protocols
42:58so these three are the sources of
43:01the information in the routing table
43:04okay
43:05so the source for each of the route in
43:07the routing table is identified
43:09by l c s
43:12o asterisk and so on okay so for now
43:15let us limit ourselves with this
43:18characters here
43:19l identifies the address assigned to the
43:22router interface
43:24okay so whatever ip address you assigned
43:26on that
43:27interface or specific router it will be
43:30noted as
43:30l in the routing table okay
43:33next c identifies a directly connected
43:37network
43:38so basically your l is just a component
43:41of c okay
43:44so l is the specific ip address assigned
43:47to the interface
43:48and that specific ip address belongs to
43:51a network
43:52c okay next
43:55is s s is for static route
43:59okay o identifies a dynamically learned
44:02network
44:03information from another router using
44:06the ospf routing protocol
44:08you also have d okay for eigrp
44:12now asterisk this route is a candidate
44:15for a default route right
44:21now in the routing tables for r1 and r2
44:25notice that the sources of each route
44:28are identified by code
44:30so the code identifies how the route was
44:32learned
44:33right for instance common codes such as
44:37the l okay the c
44:41o and then you also have there the
44:44o asterisk or the asterisk this route is
44:48candidates for a default route
44:51all right so if you'll observe
44:54see there are the directly connected
44:56networks
44:57okay so for instance 10 0 1 0
45:0110 0 1 0 is this network here
45:06all right it's directly connected to r1
45:09another one is 10
45:10020 which is this network
45:14so take note that we have three directly
45:16connected networks to r1
45:18let us evaluate that and the third one
45:21would be
45:2210 0 3 0 here okay
45:25that's 10 0 3 0. so we have three c's
45:29there
45:29these are the three directly connected
45:31networks to r1
45:33how about l l are the ip addresses
45:37assigned to a specific interface
45:40so we have also 3l here this one
45:43which is 10 0 1 1 right you've got 10
45:460 1 1 you also have
45:5010 0 2 1 then 0 2 1
45:53and the third one is 10 0
45:563 1 okay now letter o
46:00here it means dynamic routes
46:04learned from the remote networks or r2
46:10all right
46:14next on r2 now evaluating r2 here
46:19okay so we have one two
46:23three four okay so we have four
46:26directly connected networks you've got
46:28one two three
46:30four so usually the number of directly
46:33connected networks is also the number of
46:36l you have there so one two three
46:40four okay because these are the ip
46:42addresses
46:43configured on the interface okay
46:46so take note that we also have s here
46:49okay what is that
46:50s okay so the the gateway of last resort
46:54was configured so that means the default
46:55route was set on this router
46:57and that is denoted by s asset is there
47:02all right
47:07okay so routing table principles there
47:10are three routing table principles as
47:11described in the table
47:14so these are issues that are addressed
47:17by the proper configuration of dynamic
47:20routing protocols
47:22or static routes
47:26on all the routers between the source
47:27and destination devices
47:31okay so the first one would be every
47:33router makes
47:34its decision alone based on the
47:37information it has
47:39in its own routing table okay
47:43second the information in the routing
47:45table
47:46of one router does not necessarily match
47:50the routing table of another router
47:53and then third routing information about
47:56a path
47:57does not provide return routing
47:59information
48:00so you have to manually set the return
48:03trip
48:04okay if you are using static okay
48:07now if it is dynamic well let the
48:09routers discover
48:10all the possible paths okay to reach the
48:13destination
48:18okay so as network administrator
48:22it is imperative to know how to
48:24interpret the content of an ipv4
48:27and ipv6 routing tables
48:31so the figure displays an ipv4 and ipv6
48:34routing table
48:35entries on r1 for route to remote
48:38network
48:3910 0 0 okay or 10 0 for zero slash 24
48:44and
48:452001 tb8 acad
48:484 colon colon 64. both
48:52this routes were learned dynamically
48:54from ospf routing protocols
48:57okay so basically we have here okay so
49:02the information available so the first
49:04one
49:04or one there denotes a route source
49:08so this identifies how the route
49:11was learned and this is via dynamic
49:14since o
49:14is ospf and it's a dynamic routing
49:17protocol
49:19so the second one is a destination
49:21network so prefix and prefix length
49:24so this identifies the address of the
49:26remote network so this is your
49:28destination network here
49:30going to 10 0 four zeros last 24.
49:35the third one is an administrative
49:37distance this identifies the
49:39trustworthiness of the route source
49:41lower values indicate preferred route
49:44source
49:45okay so the level of believability or
49:48the level of trustworthiness
49:50is the administrative distance and in
49:52this case this is 110.
49:54ospf administrative distance is 110
49:59right now
50:02at the bottom of 110 is 50 this pertains
50:05to the metric
50:07this identifies the value assigned
50:10to reach the remote network so lower
50:13values
50:14indicate preferred routes
50:18so number five is the next tab okay this
50:21identifies the ip address of the next
50:23router
50:24to which the packet would be forwarded
50:30all right and number six
50:34is a route timestamp this identifies
50:38how much time has passed since the route
50:40was
50:41learned and the last one
50:44is exit interface this identifies
50:47the agress interface to use for the
50:49outgoing
50:51packets to reach their final destination
50:56all right so take note that the prefix
50:59length of the destination network
51:00specifies the minimum number
51:02of a far left bits that must match
51:06between the ip address of the packet and
51:09the destination network
51:10or prefix for this route to be used
51:13[Music]
51:17okay
51:21how about directly connected networks so
51:23before a router can learn about
51:25any remote networks it must have at
51:28least
51:29one active interface configured with an
51:31ip address and subnet mask
51:33or prefix length so this
51:36is known as directly connected networks
51:39or directly connected route
51:41so routers add a directly connected
51:44route to its routing table
51:45when an interface is configured with an
51:47ip address and is activated
51:50so a directly connected network is
51:52denoted by the status c
51:54in the routing table as presented
51:56earlier
51:58now the route contains a network prefix
52:00and a prefix length
52:01okay so the routing table also contains
52:04a local route
52:06for each of its directly connected
52:09networks indicated by the status code of
52:12l so
52:15also this is the ip address
52:18that is assigned to the interface on
52:21that directory connected networks which
52:23is l
52:24okay for ipv4 local routes the prefix
52:27length is 32
52:29and for ipv6 local routes the prefix
52:32length is 128
52:34okay so this means that the destination
52:37ip address of the packet
52:38must match all the bits in the local
52:41route for this route to be matched
52:44so the purpose of the local route is to
52:46efficiently determine
52:48when it receives a packet for interface
52:50instead of a packet that needs to be
52:52forwarded
52:58okay so on this output here
53:01so i put out directly connected networks
53:03are denoted by
53:05c and l so the first output here is for
53:08ipv4
53:10and the next output would be for ipv6
53:17all right so the next one is static
53:19routes
53:21so after directly connected interfaces
53:23are configured and added to the routing
53:25table
53:26static or dynamic routing can be
53:28implemented
53:29for accessing remote networks so static
53:32routes are manually configured
53:35they define an explicit path between two
53:38networking devices
53:40so unlike dynamic routing protocol
53:42static routes are not
53:44automatically updated and must be
53:47manually reconfigured if the network
53:49topology changes
53:51so the benefits of using static routes
53:53include improved
53:54security and resource efficiency so
53:57static routes
53:58use less bandwidth than dynamic routing
54:01protocols
54:02and no cpu cycles are used to calculate
54:05and communicate
54:06routes so the main disadvantages
54:09to using static router is the lack of
54:11automatic reconfiguration
54:14if the network topology changes
54:17okay so static routing has three primary
54:20uses so first it provides
54:25ease of routing table maintenance in
54:27smaller networks
54:29that are not expected to grow
54:30significantly
54:33second it uses a single default route
54:36to represent a path to any network
54:39that does not have a more specific match
54:42with another route in the routing table
54:44so default routes are used to send
54:47traffic to any destination beyond the
54:49next
54:50upstream router and
54:53it routes two and stop networks
54:57a stop network is a network accessed by
54:59single drop
55:01okay and the router has only one
55:04neighbor that stop network okay
55:11now in this example a static route
55:15can be configured on r2
55:19okay to reach
55:22the r1 network additionally because r1
55:25has
55:26only one way to send out non-local
55:29traffic
55:30a default route or a default static
55:32route can be configured on r1
55:34to point to r2 as the next hub for all
55:37other networks
55:39okay so basically the good thing about
55:41static routes this one is secure
55:44because you have to manually identify
55:47okay so the the route second
55:51this is good for small networks
55:55as it uses less resources
55:58right but then this is not an ideal
56:00solution for
56:01an enterprise network all right
56:09okay so static routes in the ip routing
56:11table so for demonstrating static
56:13routing
56:14so the topology in the figure is
56:15simplified to show only one lan attached
56:19to its router
56:20okay the figure shows ipv4 and ipv6
56:24static routes configured on
56:26r1 okay
56:30to reach 10 0 four zero and
56:332001 db8 at fours colon colon
56:3764 networks on r2 so the configuration
56:40commands
56:41are for demonstration only and are
56:44discussed in another module
56:46okay so the output shows that the ipb4
56:51and ipv6 static routing entries on r1
56:55that can reach 10 0 for zero 24
56:58and 2001 db8 i had 4
57:02colon colons 64 networks in r2
57:05so notice that both routing entries use
57:08the status code s
57:10okay when we run the show iprout command
57:14there
57:15indicating that the route was learned by
57:17static route
57:19okay so both entries also include an ip
57:22address
57:23of the next hub router via ip address
57:27okay so the static parameter at the end
57:30of the command displays
57:31only one or only static routes
57:36okay so this is it
57:44right you've got s for both ipv4 and
57:47ipv6
57:49you've got the destination network
57:51destination network
57:53and then you've got the next hub next up
57:55there
58:00okay so how about dynamic routing
58:02protocols
58:04so dynamic routing protocols are used by
58:06routers to automatically share
58:08information about the reachability
58:10and status of remote networks so dynamic
58:13routing protocols perform
58:14several activities including network
58:16discovery and maintaining routing tables
58:19so important advantages of routing or
58:22dynamic routing protocols are the
58:24ability to select
58:25a best path and ability
58:29to automatically discover a new best
58:32path
58:33when there is a change in the topology
58:35so
58:36network discovery is the ability of the
58:38routing protocol to share information
58:40about the networks
58:42that it knows about with other routers
58:46that are also using the same routing
58:48protocols so instead of depending on the
58:51manually configured static routes to
58:52remote networks on
58:54every router a dynamic routing protocol
58:56allows the routers
58:58to dynamically or automatically learn
59:01about these networks
59:02from the other routers so this networks
59:06okay and the best path to each are added
59:09to the routing table
59:10of the router and identified as network
59:14learned by specific dynamic routing
59:16protocols
59:18so the figure here shows router r1
59:22and r2 using a common routing protocols
59:25to share network information
59:28all right
59:33now in the previous example we use
59:35static routes
59:372.1040 slash 24 and 2001 db8 ahad
59:42right for colon colon slash 64 networks
59:46so this static routes are no longer
59:48configured
59:50and ospf is now being used to
59:53dynamically learn
59:54all the networks connected to r1 and r2
59:57so the following examples show an ipb
1:00:00for an ipv6 ospf
1:00:03routing entries on r1 that
1:00:06can reach this networks on r2
1:00:10okay so if you will observe it is now
1:00:12denoted by o there
1:00:14okay or ospf okay
1:00:17so notice that both routing entries
1:00:21use the status code o to indicate that
1:00:23the route was learned by
1:00:25ospf routing protocols so both
1:00:28entries also include the ip address of
1:00:30the nexup router
1:00:32via ip address
1:00:35right
1:00:39so take note that ipv6 routing protocols
1:00:42use the link local address of the
1:00:45nexthub router
1:00:47ospf routing configuration for ipv4 and
1:00:50ipv6
1:00:51are beyond the scope of this course all
1:00:54right
1:00:58okay so the next one would be the
1:01:00default route
1:01:02a default route is similar to a default
1:01:05gateway on a host
1:01:07the default route specifies the next hub
1:01:10router to use when the routing table
1:01:13does not contain a specific route
1:01:15that matches the destination ip address
1:01:17so a default route can be either
1:01:20static or learned automatically from a
1:01:22dynamic routing protocol
1:01:25so a default route has an ipv4 route
1:01:28entry of
1:01:320.0.0.0
1:01:33slash zero or an ipv6 route entry of
1:01:39colon colon slash zero so this means
1:01:42that zero or no bits need to match
1:01:46between the destination ip address and
1:01:48the default route
1:01:50okay now most enterprise routers
1:01:54have a default route in their routing
1:01:56table this is to reduce the number of
1:01:59routes
1:01:59in the routing table so a router
1:02:03such as home or small office router
1:02:06that has only one lan may reach all its
1:02:09network
1:02:10or remote networks through a default
1:02:11route this is useful when the router has
1:02:15only one directly connected networks
1:02:17and one exit point to a service provider
1:02:20router
1:02:22so in the figure here okay
1:02:25so r1 and r2 are using ospf to see our
1:02:29routing information about their networks
1:02:32okay you've got the 10 0 x x 24
1:02:36and then you've got the 2001 db8 account
1:02:39x
1:02:40slash 64.
1:02:43so r2 has the static route to the isp
1:02:49okay and then r2 will forward any
1:02:52packets with destination ip address
1:02:55that does not specifically match one of
1:02:57the networks in its routing table
1:02:59to the isp router so this would include
1:03:03all packets distinct
1:03:05to the internet
1:03:10okay so next r2
1:03:13has a default static route to the isp
1:03:16router
1:03:17and then the default route is advertised
1:03:19by r2 to r1
1:03:21using dynamic routing protocol ospf
1:03:24so r2 has shared its default route with
1:03:28r1 using
1:03:30ospf okay so r1
1:03:34will now have a default route in its
1:03:36routing table
1:03:38that it specifically match one of the
1:03:41networks
1:03:42in its routing table to r2
1:03:47okay okay so
1:03:50here's the sample output of the default
1:03:53route
1:03:54okay default route on r2
1:03:57okay loaded by s asterisk you've got
1:04:00here 0.0.0 the zeros that's
1:04:03zero and a default route also on r2 for
1:04:06ipv6 which is colon colon slash
1:04:09zero there all right
1:04:17okay so how about the structure of an
1:04:20ipb for routing table
1:04:23so ipb4 was standardized in the early
1:04:251980s
1:04:26during the now obsolete classful
1:04:28addressing architecture
1:04:31so the ipv4 routing table is organized
1:04:34using
1:04:34this same class full structure
1:04:38in the show ip route output notice that
1:04:41some route entries are left justified
1:04:45where others are indented
1:04:48okay so this is based on how the routing
1:04:50process
1:04:52searches the ipb for routing table for
1:04:54the longest match
1:04:56so this was all because of classful
1:04:58addressing
1:05:00so although the lookup process no longer
1:05:03uses classes
1:05:04okay so the structure of the ipv routing
1:05:07table still remains in this
1:05:09format
1:05:13okay so although the details of the
1:05:16structure are beyond the scope this
1:05:18module
1:05:19it is helpful to recognize the structure
1:05:22of the table
1:05:23okay so as indented entry is known
1:05:26as a child route
1:05:31okay so
1:05:34you'll have this dented right
1:05:38on the routing table so an indented
1:05:41entry is known as a child route
1:05:43a route entry is indented
1:05:46if it is the subnet of a classful
1:05:48address class a b
1:05:49or c network so directly connected
1:05:52networks will always be
1:05:54indented okay or child routes because
1:05:57the local address of the interface is
1:05:59always entered
1:06:01in the routing table as slash 32
1:06:05so the child route will include the
1:06:07route source
1:06:09and all the forwarding information such
1:06:11as the next hub address
1:06:12okay so the classful network address
1:06:16of this subnet will only be shown above
1:06:18the route entry
1:06:20less indented and without a source code
1:06:23so the route is known as the parent
1:06:26route
1:06:27okay so this is just a brief
1:06:30introduction to the structure of an ipv4
1:06:32routing
1:06:33table and does not cover details of the
1:06:36specifics
1:06:37of this architecture
1:06:40okay so if you will observe from the
1:06:42output here
1:06:44192.168.1.0 is variably subnetted
1:06:49okay 192.168.1.04
1:06:52and under that okay so this four
1:06:56here are indented so these are the child
1:06:59or children and this is the parent okay
1:07:02so that's the structure of
1:07:04an ipp for routing table
1:07:09okay so in this example
1:07:13shows the ipb4 routing table for r1 in
1:07:16the topology
1:07:17notice that all of the networks in the
1:07:20topology are subnets
1:07:21so which are child routes
1:07:24okay and then these are child routes of
1:07:28the class a network
1:07:30and the parent route 10 0
1:07:340 0 so all of these are
1:07:37child routes right and then you've got
1:07:39the parent route there
1:07:43now how about for ipv6 so the concept of
1:07:47classful addressing was never part
1:07:49of ipv6 so the structure of an ipv6
1:07:52routing table is very straightforward
1:07:54so every ipv6 route entry is formatted
1:07:58and aligned
1:07:59the same way all right
1:08:06okay so next would be the administrative
1:08:08distance
1:08:10okay so from the previous course you
1:08:13have in cisco
1:08:14administrative distance pertains to the
1:08:16level of trustworthiness or the
1:08:18believability
1:08:20okay so a route entry for a specific
1:08:22network address or prefix or prefix
1:08:24length
1:08:25can only appear once in the routing
1:08:28table
1:08:28however it is possible that the routing
1:08:31table learns about the same network
1:08:33address
1:08:34from other than one routing source
1:08:37except for a very specific circumstances
1:08:40only one dynamic routing protocol should
1:08:43be implemented on a router however
1:08:45it is possible to configure both ospf
1:08:48and eigrp on the router and both
1:08:52running okay or both routing protocols
1:08:55may learn the same destination network
1:08:58so each protocol or routing protocols
1:09:01may decide on a different path
1:09:03to reach the destination based on the
1:09:05metric of the routing table
1:09:08so this raises a few questions about
1:09:12or such as the following okay so how
1:09:15does the router know
1:09:17which source to use or which route
1:09:21should it install in the routing table
1:09:24okay now cisco ios uses
1:09:28what is known as the administrative
1:09:29distance or ad
1:09:31to determine the route to install into
1:09:34the ib routing table
1:09:36so the ad or administrative distance
1:09:38represents the trustworthiness
1:09:41okay so the lower the ad the more
1:09:44trustworthy
1:09:46okay so because eigrp has an id of 90
1:09:50and though spf has an id of 110
1:09:53the eigrp route entry would be installed
1:09:56in the routing table
1:09:58all right so the ad does not necessarily
1:10:01represent
1:10:02which dynamic routing protocol is best
1:10:08now take a look at the table here so
1:10:11a more common example is a router
1:10:13learning the same
1:10:14network address from the static route
1:10:17and dynamic routing protocol such as
1:10:19ospf
1:10:20so a static route has an id of one
1:10:25okay so directly connected is of course
1:10:27zero
1:10:29right so
1:10:32ospf has an id of
1:10:37110 okay now when a router has the
1:10:41choice of
1:10:42static okay and ospf route
1:10:46the static route takes precedence
1:10:49so directly connected networks have the
1:10:51lowest id of zero
1:10:53only directly connected networks can
1:10:56have an
1:10:57id of zero right so this table
1:11:00summarizes
1:11:02the routing protocols and their
1:11:03associated administrative distance all
1:11:12right so how about static and dynamic
1:11:14routing
1:11:15okay are we going to use static or
1:11:18dynamic which one is for us
1:11:20okay now the previous topic discussed
1:11:22the ways
1:11:23that router creates its routing tables
1:11:27so you now know that routing like ip
1:11:30addressing
1:11:31can be either static or dynamic should
1:11:34you use static or dynamic routing
1:11:37the answer is both okay so static and
1:11:40dynamic routing are not mutually
1:11:42exclusive
1:11:43rather most network user combinations
1:11:47of dynamic routing protocols and static
1:11:49routes
1:11:51now for static routes static routes
1:11:54are commonly used in the following
1:11:56scenarios
1:11:58so as a default route forwarding packets
1:12:00to a service provider
1:12:02second for routes outside the routing
1:12:05domain
1:12:06and not learned by dynamic routing
1:12:08protocol
1:12:10next is when the network administrator
1:12:13wants to explicitly define the path
1:12:16for a specific network we use static
1:12:19and for routing between stop network we
1:12:22use static
1:12:24so static routes are useful for smaller
1:12:26networks with only one path
1:12:29to an outside network they also provide
1:12:32security
1:12:32in larger network for certain types of
1:12:34traffic
1:12:36or links to other networks
1:12:40that need more control
1:12:44now for dynamic routing dynamic routing
1:12:47protocols
1:12:48help the network administrator manage
1:12:50the time consuming and exactly
1:12:52or extracting process of configuring and
1:12:55maintaining static routes
1:12:58okay so dynamic routing protocols are
1:13:01implemented
1:13:02in any type of network consisting of
1:13:07more than one just more than just a few
1:13:10routers
1:13:11okay so dynamic routing protocols are
1:13:14scalable
1:13:15and automatically determine better
1:13:17routes
1:13:18if there is a change in the topology
1:13:21so dynamic routing protocols are
1:13:23commonly used in the following scenarios
1:13:25so in networks
1:13:26consisting of more than
1:13:30few routers when a change in the network
1:13:33topology requires the network to
1:13:35automatically determines another path
1:13:37then dynamic routing protocol is a good
1:13:40choice
1:13:41and for scalability as the network grows
1:13:45the dynamic routing protocol
1:13:46automatically learns
1:13:48about new networks
1:13:52okay now the table here shows a
1:13:55comparison of some of the differences
1:13:57between dynamic and static routing
1:14:00okay so dynamic routing would be
1:14:04good for an enterprise network
1:14:08so automatically adapts to topological
1:14:10changes
1:14:12scalability will suitable for simple to
1:14:14complex network topologies
1:14:16security must be configured when you use
1:14:18dynamic routing protocol
1:14:21resource utilization well
1:14:24when it comes to research utilization
1:14:26dynamic is high
1:14:29past predictability well that's the
1:14:31advantage of dynamic routing protocol
1:14:34okay now for static so
1:14:37the complexity of the configuration
1:14:39increases as the network size increases
1:14:43so for topological changes the
1:14:46administrator needs to manually
1:14:48configure
1:14:48or there should be a manual intervention
1:14:51needed
1:14:54scalability well static is suitable for
1:14:57small networks
1:14:58security is inherent all right
1:15:02so no additional resources are needed
1:15:05and explicitly defined by the
1:15:07administrator for pro
1:15:08pass predictability so it is recommended
1:15:13that we have to use or we use dynamic
1:15:16routing along with static
1:15:18routing and vice versa
1:15:23all right so let us cover here a dynamic
1:15:27routing evolution okay
1:15:30so dynamic routing protocols have been
1:15:33used in the networks
1:15:34since the late 1980s okay one of the
1:15:38first routing protocol was
1:15:39rip rip version 1 was released in 1988
1:15:44but some of the basic algorithms within
1:15:46the protocol were used in advanced
1:15:48research
1:15:49project agency network or arpanet in
1:15:53early 1969 okay
1:15:56now as the networks evolved and become
1:15:59more complex
1:16:00new routing protocols emerged the rip
1:16:03protocol
1:16:04was updated to reap version 2 to
1:16:06accommodate growth in the network
1:16:08environment
1:16:10so however okay
1:16:14however this network needs to be
1:16:17upgraded okay and we have the increase
1:16:20in terms of
1:16:21users and the number of workstations on
1:16:24the network
1:16:26okay so rip version two still has
1:16:29not scaled to the larger network
1:16:32implementations
1:16:33of today so to address the needs of
1:16:36larger networks
1:16:38two advanced routing protocols were
1:16:40developed
1:16:41you've got the ospf and the intermediate
1:16:44system
1:16:44to intermediate system or isis
1:16:48okay and then cisco developed the
1:16:51interior gateway erratic protocols or
1:16:53igrp
1:16:55which was then replaced by enhanced
1:16:58igrp or we call it eigrp okay
1:17:02so which also scales well in a large
1:17:04network implementations
1:17:07so additionally there was the need to
1:17:09connect
1:17:10the different routing domains of
1:17:12different organizations
1:17:14and provide routing information between
1:17:16them
1:17:17so the border gateway or bgp
1:17:20was established okay so
1:17:24the bgp the successor of the exterior
1:17:28gateway protocol or egp
1:17:30is used between the isps okay
1:17:33or internet service providers so bgp is
1:17:37also known as
1:17:39the exterior gateway protocol
1:17:42or egp okay when say bgp
1:17:46is either ebgp and ibgp where in
1:17:50bgp is popularly known as ebgp
1:17:54okay and we have now
1:17:59ospf version 3 and 1999
1:18:02okay and then 2 000 onwards in 2008
1:18:05you've got isis
1:18:06version 6.
1:18:10okay next the table classifies
1:18:14the current routing protocols interior
1:18:17gateway protocols or igps
1:18:19these are routing protocols used to
1:18:20exchange routing information within the
1:18:22routing domain
1:18:24administered by a single organization
1:18:27so there's only one egp and that
1:18:30is bgp okay
1:18:33so bgp is used to exchange routing
1:18:35information between different
1:18:37organizations
1:18:38known as autonomous systems or aes
1:18:41so bgp is used by isps
1:18:45to route packets over the internet so
1:18:48distance vector
1:18:49link state and pass the vector are
1:18:52protocols okay so
1:18:54under interior gateway protocols
1:18:58okay so basically from this table we can
1:19:01classify routing protocols are igp
1:19:04or as igp and egp interior
1:19:08these are used within the organization
1:19:10within the control of a single
1:19:12administrator
1:19:13and egp is basically used okay
1:19:17on
1:19:20the isps are among isps all right
1:19:24so further we can divide routing
1:19:26protocols into distance vector
1:19:28link state and pass vector so under pass
1:19:30vector you only have bgp
1:19:32there link state you've got ospf and
1:19:35isis
1:19:36and then distance vector clip
1:19:39okay and eigrp
1:19:49okay so next would be dynamic routing
1:19:51protocol concepts
1:19:53so a routing protocol is a set of
1:19:55processes algorithms
1:19:57and messages that are used to exchange
1:20:00routing information and populate the
1:20:01routing table
1:20:03with a choice of best path
1:20:06so the purpose of dynamic routing
1:20:08protocols includes the following
1:20:10so discovery of the remote networks
1:20:12maintaining an up-to-date routing
1:20:14information
1:20:15choosing the best path to destination
1:20:17networks
1:20:18and ability to find new best paths if
1:20:21the current path is no longer available
1:20:26so the main components of the routing or
1:20:29dynamic routing protocols includes the
1:20:31following so it has data structures
1:20:34okay so routing protocols typically use
1:20:37tables or databases for their operations
1:20:41this information is kept in a ram you
1:20:44also have the routing protocol messages
1:20:47routing protocol use various types of
1:20:49messages to discover neighbor routers
1:20:52exchange routing information and other
1:20:54tasks
1:20:55to learn and maintain accurate
1:20:57information about the network
1:21:01so the next one is algorithm an
1:21:03algorithm
1:21:04an algorithm is a finite list of steps
1:21:08used to accomplish a task that was the
1:21:10definition in programming right
1:21:12so routing protocols use algorithms
1:21:16for facilitating routing information
1:21:20and for the best path determination
1:21:23okay so routing protocols allow routers
1:21:26to dynamically share information
1:21:28about remote networks and automatically
1:21:31offer this information
1:21:33to their own routing tables
1:21:39okay so in here routing protocols
1:21:43allow routers to dynamically share
1:21:46information about remote networks and
1:21:49automatically
1:21:50offer this information to their own
1:21:52routing tables
1:21:53as shown here okay so routing protocols
1:21:57determine the best path or route
1:22:00to each network so the route is then
1:22:03offered
1:22:04to the routing table the route will be
1:22:07installed in the routing table if there
1:22:09is
1:22:09not another routing source with a lower
1:22:12ad
1:22:14so a primary benefit of a routing or
1:22:17dynamic routing protocol is that the
1:22:19router exchange
1:22:20routing information when there is
1:22:22topological changes there's a good thing
1:22:24about it
1:22:25so this exchange allows routers to
1:22:28automatically learn
1:22:29about new networks and to find alternate
1:22:32paths
1:22:33when there is a link failure to your
1:22:35current network
1:22:39okay how about the best path before best
1:22:42part or before a pass
1:22:44to a remote network is offered to the
1:22:46routing table
1:22:47the dynamic routing protocol must
1:22:49determine the best path
1:22:50to the network so determining the best
1:22:53path
1:22:54may involve the evolution of multiple
1:22:56paths
1:22:57to the same destination network and
1:22:59selecting the optimum
1:23:01or the shortest path to reach that
1:23:03network
1:23:04so whenever multiple paths to the same
1:23:07network exist
1:23:09which path uses different exit interface
1:23:13on the router
1:23:14to reach that network so the best pass
1:23:18is selected by routing protocol based on
1:23:20the value or metric it uses
1:23:22to determine the distance to reach the
1:23:25network
1:23:26so a metric is a quantity value or
1:23:29quantitative value
1:23:31used to measure the distance to a given
1:23:33network
1:23:35so the network okay or the path
1:23:38or best path to the network is the path
1:23:41with the lowest
1:23:42metric okay so dynamic routing protocols
1:23:46typically use their own rules
1:23:48and metrics to build and update routing
1:23:51tables
1:23:53all right so the routing algorithm
1:23:56generates a value
1:23:57and a metric for its path through the
1:24:01network
1:24:02so metrics can be based on either
1:24:05a single characteristics or several
1:24:07characteristics of
1:24:09a path so some routing protocols can be
1:24:12based okay or can
1:24:16base route selection on multiple metrics
1:24:19so combining them into a single metric
1:24:22okay
1:24:23so the following table lists the common
1:24:26dynamic routing protocols and their
1:24:28metrics
1:24:30so basically rip or the routing
1:24:32information protocol
1:24:34their metric is based on the hub counts
1:24:38and the maximum of 15 healths
1:24:42okay allowed next
1:24:45you've got ospf the metric is
1:24:49based on the cost okay so faster links
1:24:52are assigned lower costs
1:24:56and then the eigrp it calculates a magic
1:25:00based on the slowest bandwidth and delay
1:25:03values
1:25:04okay it could also include load
1:25:08and reliability into the metric
1:25:11calculations
1:25:14so we will be discussing this as we
1:25:15progresses with this
1:25:18uh course
1:25:22all right so the animation in the figure
1:25:25highlights how the path
1:25:26may be different depending on the magic
1:25:29being used
1:25:30so if the path fails the dynamic routing
1:25:34protocol
1:25:35will automatically select a new path
1:25:38if one exists all right
1:25:54okay so that's how it works
1:25:58next is load balancing what is load
1:26:00balancing
1:26:02what happens if a routing table has two
1:26:05or more paths
1:26:06with identical metrics to the same
1:26:08destination network
1:26:10okay so when a router has two or more
1:26:13paths
1:26:14to a destination with equal cost metrics
1:26:17then the router forwards the packet
1:26:19using both
1:26:21paths equally so this is called equal
1:26:24cost load balancing so the routing table
1:26:27contains the single destination network
1:26:30but has multiple exit interfaces
1:26:33one of each equal cost path
1:26:37so the router forwards packet using
1:26:39multiple exit interfaces
1:26:41listed in the routing table so if
1:26:44configured correctly
1:26:46load balancing can increase the
1:26:48effectiveness and performance
1:26:50of the network so equal cost load
1:26:53balancing is implemented
1:26:55automatically by dynamic routing
1:26:57protocols
1:27:01so it is enabled with static routes
1:27:06when there are multiple static routes to
1:27:09the same destination network
1:27:10using the different nexup routes
1:27:14so only eigrp supports an equal cost
1:27:17load balancing
1:27:25okay so take a look at this so our
1:27:28packet traverses
1:27:30going to the destination or same
1:27:32destination
1:27:33using different paths here some goes on
1:27:3752 mbps
1:27:38top right so that's the first one and
1:27:41some also uses the 52 mbps connections
1:27:44between r2 and
1:27:46r3 okay so this is what you call
1:27:50load balancing okay so
1:27:53the the device or routers uses all the
1:27:57available paths
1:27:58to get into the destination
1:28:01right so
1:28:04that's the end of the video lecture
1:28:06thanks for watching and listening have a
1:28:08great day

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