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Structuring and Modularizing the Network Part 1 — Transcript

by Santelmo · 2,906 words · 644 segments · language en · Watch on YouTube

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0:04hi hello there
0:06welcome to structuring and modularizing
0:08the network
0:09this video introduces a modular
0:12hierarchical approach to network design
0:14the cisco enterprise architecture from
0:17the last
0:18video we talked about applying
0:20methodology to a design
0:22this video begins with a discussion of
0:24the hierarchical network structure
0:27the next section introduces network
0:29modularization
0:31and discusses the details of the cisco
0:33enterprise architecture
0:35following that are the detailed
0:37description of services
0:39within modular networks and a discussion
0:42of
0:42network management protocols and
0:44features
0:46let's get started
0:51this video lecture will talk about
0:54network hierarchy
0:55using a modular approach to network
0:58design
0:59services within modular networks
1:02network management protocols and
1:05features
1:06and at the end of this video lecture we
1:08are going to summarize
1:09each of the module and the entire
1:12structuring and modularizing network
1:14topic
1:19network hierarchy
1:23this section explains the hierarchical
1:26network model
1:27which is composed of the access
1:30distribution
1:31and core layers the functions generally
1:34associated
1:36with each of these layers are discussed
1:40as this is the most common approach to
1:43designing a hierarchical network
1:45historically it is used in the design of
1:48the enterprise
1:49local area network and wide area network
1:51data networks
1:53this model works equally well
1:56within the functional modules of the
1:58cisco enterprise architecture
2:01these modules are discussed later in
2:03this video
2:05in section using a modular approach to
2:08network design
2:13hierarchical network design layers so as
2:15shown here in the figure
2:17the hierarchical network design model
2:19consists of
2:20three layers you've got the access layer
2:24which provides the local and remote work
2:28group or user access to the network
2:32next would be the distribution layer
2:34which provides
2:35a policy-based connectivity and
2:38a core layer or a backbone which
2:41provides high-speed transport to satisfy
2:44the connectivity
2:45and transport needs of the distribution
2:48layer devices
2:50so each hierarchical layer focuses on
2:53specific functions
2:54thereby allowing the network designer to
2:57choose the right systems
2:59and features based on their function
3:02within the model
3:04so this approach helps provide more
3:07accurate capacity planning
3:09and minimize total costs
3:15let's have an example so this figure
3:17here illustrates a sample network
3:19showing the mapping of the hierarchical
3:21models
3:21three layers so again these are the axis
3:25layer
3:25the distribution layer and the core
3:28layer
3:29you do not have to implement the
3:30hierarchical layers as distinct
3:33physical entities they are defined to a
3:36successful network design and to
3:38represent functionality
3:40that must exist within a network
3:44so the actual manner in which you
3:46implement the layers
3:47depends on the needs of the network you
3:49are designing
3:51each layer can be implemented in routers
3:55or switches represented by physical
3:58media or combined
4:00in a single device so a particular layer
4:03can be omitted but hierarchy should be
4:06maintained
4:07for optimum performance the following
4:10sections
4:11details the functionality of the three
4:13layers
4:14and the devices used to implement them
4:19let's start with the access layer access
4:22layer functionality
4:23so basically this section describes the
4:26access layer functions
4:28and the interaction of the access layer
4:31with
4:31the distribution layer and local or
4:34remote
4:35users so the role of the apps layer
4:39is basically the access layer is the
4:42concentration point
4:43at which clients access the network
4:48access layer devices control traffic by
4:50localizing
4:51service requests to the access media
4:54the purpose of the atlas layer is to
4:56grant user access to network resources
5:00so following are the access layer
5:02characteristics
5:04so in the campus environment the access
5:07layer typically incorporates
5:08switched lan devices with ports that
5:12provide connectivity for workstations
5:14and servers so in the one environment
5:18the access layer for teleworkers or
5:20remote sites
5:21provides access to the corporate network
5:23across
5:24some wide area technology such as the
5:27old
5:28frame relay multi-protocol label
5:31switching or the mpls
5:33you also have the integrated services
5:35digital network or isdn
5:38list lines digital subscribers line or
5:41dsl
5:42over traditional um telephone copper
5:45lines or two axle cable and
5:48of course other new technologies that we
5:50have now
5:51so as not to compromise network
5:53integrity
5:54access is granted only to authenticated
5:57users
5:58or devices such as those with physical
6:02address or logical name authentication
6:04for example the devices at the access
6:08layer must detect
6:10whether a telecommuter who is dialing in
6:13is a legitimate user yet they must
6:16require
6:17minimal authentication steps for the
6:19telecommuters
6:22so layer 2 switching and the multi-layer
6:25switching in the access layer
6:27so access can be provided to access
6:31users as part of either a layer 2 or l2
6:34switching environment
6:35or a multi-layer switching environment
6:38also known as
6:39layer 3 switching now
6:43using a layer 2 switching in the access
6:45layer
6:46access to local workstations and servers
6:49can be provided
6:50using a shared or a switched media lens
6:54or local area networks
6:56you also have vlans or the virtual local
6:58area networks
6:59which may be used to segment the
7:01switched lens
7:03so each lan or vlan is a single
7:06broadcast domain
7:08so the axis layer aggregates and user
7:11switched
7:1210 over 100 ports and provides fast
7:16ethernet pass easter channel or giga
7:19internet uplinks
7:21to the distribution layer to satisfy
7:22connectivity requirements
7:24and reduce the size of the broadcast
7:27domains
7:29you can deploy multiple vlans with its
7:32own
7:32ip subset and its own instance of
7:35spanning tree protocol or stp
7:37providing alternative path in case of
7:41failure in this case layer 2 trunking
7:45so typically using the ieee 802.1 q
7:49trunking protocol is used between the
7:51axis layer
7:53switches and the distribution layer
7:56switches
7:57with per vlan stp on each uplink
8:00for load balancing and redundancy and
8:04with a distribution layer multi-layer
8:06switch providing
8:08the interval and communication for the
8:10access layer
8:12so the key point would be a recommended
8:15best practice
8:16is to implement one vlan thus
8:19supporting one ip subnet per access
8:22switch
8:23to connect the access switches to the
8:26distribution switches
8:28with a layer 3 links rather than trunks
8:33when rsdp cannot be implemented the
8:35cisco ios stp features such as uplink
8:38fast
8:39part fast and backbone fast can be used
8:42to provide equivalent convergence
8:43improvements
8:44so these features are described as
8:47follows
8:48uplink fast enables faster fill over
8:51on access layer switch on which a dual
8:55uplinks connect to the distribution
8:56layer
8:57the failover time is reduced by
8:59unblocking the black uplink port
9:01on a switch immediately after the root
9:03work failure
9:05so thereby transitioning it to the
9:07forwarding state
9:08immediately without transitioning the
9:11port through the listening and learning
9:12states
9:14next would be the backbone fast if a
9:17link
9:17fails on the way to the root switch but
9:19is not directly connected
9:21to the local switch backbone fast
9:24reduces the convergence times
9:25from 50 seconds to between something
9:28like 20
9:29and 30 seconds and the last one would be
9:34wordfast enable switch ports connected
9:37to a non-switch
9:38devices such as workstations to
9:41immediately enter the spawning tree
9:43forwarding state
9:44thereby bypassing the listening and
9:46learning states
9:48when they come up so that is where the
9:51forecast
9:51will take over so ports connected only
9:55to
9:56an end user device workstations
9:59computers
10:00do not have bridging loops so it is safe
10:02to go directly
10:04to the forwarding state significantly
10:06reducing the time it takes
10:07before the port is unusable so if you
10:10want to learn more about
10:11this stp you could go ahead and check
10:13the supplementary videos about stp
10:17now using a multi-layer switching in the
10:20access layer
10:22the most common design for remote users
10:25is to use multi-layer switches or
10:28routers
10:29so a multi-layer switch or router is the
10:32boundary for broadcast domains and is
10:35necessary
10:36for communicating between broadcastmates
10:38including vlans
10:40so access routers provide access
10:43to remote office environments using
10:45various
10:46wide area technologies combined with
10:49multi-layer features such as
10:50route propagation packet filtering
10:54authentication security
10:57and of course the qos or the quality of
10:59service
11:01so these technologies allow the network
11:04to be optimized to satisfy a particular
11:07user's
11:08needs in dial-up connection
11:12dial on demand or the ddr okay
11:15and static routing can be used to
11:18control
11:18costs
11:23let's have an atlas layer example here
11:25so this figure
11:26illustrates a simple network
11:29in which the compass access layer
11:32aggregates
11:33and users and provides uplinks to the
11:36distribution layer
11:38so the access layer switches are dual
11:41attached
11:41to the distribution layer switches for
11:44high availability
11:46the access layer can support convergence
11:49high availability security
11:52quality of service or qos and ip
11:55multicast
11:56so some services found at the access
12:00layer include establishing
12:01a quality of service trust boundary or
12:04the qos
12:05trust boundary broadcast suppression
12:09and the internet group management
12:11protocol or igmp snooping
12:14so in here workstations are attached to
12:17vlans with layer 2 switches
12:19so the recommended practice implement
12:22one villain
12:23that means one ip subnet
12:26per access switch so access switches
12:30connects to layer 3 links
12:32if only one vlan per access switch or
12:35via
12:36vlan trunking okay so if needed a
12:39distribution router's
12:40route between virtual local area network
12:46let's talk about distribution layer
12:49this section describes distribution
12:52layer functions
12:53and the interaction of the distribution
12:55layer
12:56with the core and the access layers
13:00so the role of the distribution layer
13:02basically
13:04it represents both a separation between
13:06the axis and the core layers
13:08and a connection point between the
13:11diverse access sites
13:12and the core layer the distribution
13:15layer determines
13:16department or workgroup access and
13:19provides
13:20policy-based connectivity so following
13:23are the characteristics
13:24of the distribution layer so
13:27distribution layer devices
13:29control access to resources that are
13:32available at the core layer
13:34and must therefore use bandwidth
13:36efficiently
13:38in a campus environment the distribution
13:40layer aggregates
13:42wiring closet or the telecommunication
13:44closes bandwidth
13:45by concentrating multiple low-speed
13:48access
13:49links into high-speed cordling and using
13:52switches
13:53to segment work groups and isolate
13:56network problems
13:57to prevent them from affecting the core
13:59layer
14:01so similarly in a one environment the
14:04distribution layer aggregates
14:07one connections at the edge of the
14:08campus and
14:10provides policy-based connectivity
14:13this layer provides redundant
14:15connections for access devices
14:17redundant connections also provide the
14:19opportunity
14:21to load balance between devices
14:24so the distribution layer represents a
14:26routing boundary
14:28between the access and the core layers
14:30and is where
14:31routing and packet manipulations are
14:33performed
14:35so the distribution layer allows the
14:37core layer to connect
14:38diverse sites while maintaining high
14:40performance
14:42so to maintain good performance in the
14:44core
14:45the distribution layer can redistribute
14:48between
14:49a bandwidth intensive access layer
14:51routing protocols
14:53and optimized core routing protocols
14:57so route filtering is also implemented
15:00at the distribution layer
15:02the distribution layer can summarize
15:04routes from the axis layer
15:06to improve routing protocol performance
15:09so for some networks the distribution
15:12layer offers a default route
15:14to access layer routers and run dynamic
15:17routing protocols
15:18only when communicating with core
15:21routers
15:23the distribution layer connects network
15:25services
15:26to the access layer and implements
15:28policies
15:29for the quality of service security
15:32traffic loading
15:33and routing so for example
15:37the distribution layer addresses
15:40different protocols quality of service
15:42needs
15:43by implementing policy-based traffic
15:45control
15:46to isolate backbone and the local
15:49environments
15:50so policy-based traffic control
15:53prioritizes
15:54traffic to ensure the best performance
15:57for the most
15:58time critical and time dependent
16:01applications
16:03so the distribution layer is often
16:06the layer that terminates the access
16:08layer vlans
16:09broadcastmates however this can also be
16:13done at the axis layer
16:15so this layer provides any media
16:18transitions for example between ethernet
16:21and the one technology okay so that must
16:24occur
16:26so this includes policy based
16:29connectivity
16:30so when you say policy based
16:32connectivity this means
16:34implementing the policies of the
16:35organization
16:37as described in applying a methodology
16:40to a network design video so what are
16:43the methods
16:44for implementing policies so this
16:46includes
16:48filtering by source and destination
16:51address
16:52filtering based on input and output
16:55ports
16:57hiding internal network numbers by route
17:00filtering
17:02providing specific static routes rather
17:04than using routes
17:05from a dynamic routing protocol for
17:08security okay so you could have for
17:11example certain packets
17:13might not be allowed into a specific
17:15part of the network
17:17so you also have the quality of service
17:19mechanisms for example
17:21the precedence and the type of service
17:24or tos okay so or the value
17:28in ip packet headers can be set in
17:31routers to leverage
17:32viewing mechanisms to prioritize
17:35traffic so basically
17:39the distribution layer provides link
17:42between the core
17:43and the access layer
17:48let's have the distribution layer
17:49example so this figure
17:52shows a sample network with various
17:54features of the distribution layer
17:57so following are the characteristics of
17:59the distribution layer
18:00in the routed compost network shown in
18:03the figure
18:05so the multi-layer switching is used to
18:09forward the packets
18:12going to the access layer and in this
18:14case
18:15within the access layer so multi-layer
18:18switching is performed
18:20in the distribution layer and extended
18:22towards
18:23the core layer the distribution layer
18:28performs a two-way route or a
18:29distribution to exchange the routes
18:32between the routing information protocol
18:35version two
18:36okay so which is represent two okay
18:39and enhanced interior gateway routing
18:41protocols
18:43or the eigrp routing processes
18:46so this could be any routing protocol so
18:49it could be ospf and digrp and vice
18:52versa
18:52it could be any routing protocols
18:55now route filtering is configured on the
18:58interfaces
18:59towards the access layer
19:03route summarization is configured on the
19:06interfaces
19:07towards the core layer
19:10the distribution layer contains highly
19:13redundant connectivity
19:15both towards the axis layer and towards
19:19the core layer
19:23now let's talk about the core layer
19:26the core layer functionality so this
19:28section describes
19:30core layer functions and the interaction
19:33of the core layer
19:34with the distribution layer so the role
19:37of the core layer
19:39the function of the core layer is to
19:41provide fast and efficient
19:43data transport so characteristics of the
19:47core layer includes the following
19:49so the core layer is a high speed
19:53backbone that should be designed
19:56to switch packets as quickly as possible
19:59to optimize
20:00communication transport within the
20:02network
20:04because the core is critical for
20:06connectivity the core layer devices are
20:08expected to provide a high level
20:11of availability and reliability
20:14a fault tolerant network design ensures
20:17that
20:17failures do not have a major
20:20impact on network connectivity
20:24the core must be able to accommodate
20:27failures
20:28by rerouting traffic and responding
20:30quickly to changes in network topology
20:34the core must provide a high level of
20:36redundancy
20:38a full mesh is strongly suggested
20:41and at least a well connected partial
20:44mesh
20:45with multiple paths from each device
20:48is required so the core layer should not
20:52perform
20:53any packet manipulation okay so such
20:56as checking access lists or filtering
21:01which would slows down the switching of
21:03packets
21:05so the core layer must be manageable
21:08the core devices must be able to
21:11implement
21:11scalable protocols and technologies
21:15and provide alternative paths and
21:18load balancing
21:23so let's have an example of the
21:24switching or multi-layer switching in
21:27the campus core
21:29so layer to switching or a multi-layer
21:32switching
21:32which is also known as a layer 3
21:36switching or routing can be used in the
21:39core layer
21:41so because core devices
21:44are responsible for accommodating
21:47failures
21:48by rerouting traffic and responding
21:50quickly to the network topology changes
21:53and because performance for routing in
21:55the core
21:56with a multi-layer switch incurs no cost
22:00most implementations have a multi-layer
22:03switching
22:04in the core layer so the core layer can
22:07be then
22:07more readily implement scalable
22:09protocols and technologies
22:12and provide alternate path and
22:15load balancing so the figure shows an
22:18example of a layer 2 switching
22:21in the compass core so in the figure
22:25the typical packet between access sites
22:28follows these steps so step one
22:32basically the packet is a layer two
22:36switched towards the distribution layer
22:41okay or the distribution switches here
22:44step two the distribution switch
22:46performs
22:47multi-layer switching towards the core
22:49interface
22:52okay now step three the packet
22:55is a layer to switch across the lan cord
22:59the distribution uh receiving
23:03switches performs multi-layer switching
23:05towards
23:06an access land or at the access layer
23:08land here
23:10okay this uh step number four and step
23:12five
23:13the packet is a layer to switch across
23:16the access layer land to the destination
23:19hosts connected to this
23:21layer two switches here
23:27so routing in the one network so this
23:30figure here
23:31shows an example of a multi-layer
23:33switching in the campus core
23:36so this is a typical packet between
23:38access sites
23:39follows the steps here so basically step
23:42one
23:44the packet is layer two switch towards
23:47the distribution
23:48layer for the distribution switches
23:52okay step two the distribution switch
23:55performs
23:56multi-layer switching towards a core
23:59interface
24:01and then the packet is multi-layer
24:03switched across the lan core
24:06step four the receiving distribution
24:08switch performs
24:09a multi-layer switching towards the
24:11access lane
24:13okay or towards the axis layer and then
24:16last one would be the packet is layered
24:19to switch
24:20across this access layer land to the
24:23destination hosts connected to this
24:25layer 2 switches here
24:30now to summarize the hierarchical
24:33network model provides
24:34a modular view of a network
24:38making it easier to design and build the
24:40network
24:42the purpose of the access layer is to
24:44grant
24:45end user access to network resources
24:50the distribution layer provides
24:52aggregation
24:53for the access layer devices and uplinks
24:57to the core layer devices it is also
25:00used in force
25:01policy within the network and then the
25:04core layer provides a high speed
25:06high available backbone designed to
25:09switch
25:09packets as fast as possible

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