ccna dis3 - chapter 5 - routing with a distance vector protocol_ppt [compatibility mode]

8/3/2019 CCNA Dis3 - Chapter 5 - Routing With a Distance Vector Protocol_ppt [Compatibility Mode]

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Chapter 5 Routing witch a DistanceVector Protocol

CCNA Discovery 4.0


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Intruduction

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Intruduction



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Intruduction



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Intruduction



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Objectives


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ManagingEnterprise

Networks


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Enterprise Networks


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Enterprise Networks

Routers forward traffic and prevent broadcasts from clogging the mainchannels to crucial services.

Enterprise networks provide a high level of reliability and services. To ensurethis, network professionals:

Design networks to provide redundant links to use in case a primary datapath fails.

Deploy Quality of Service (QoS) to ensure critical data receives prioritytreatment.

Use packet filtering to deny certain types of packets, maximize availablebandwidth, and protect the network from attacks.


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Enterprise Topologies

Choosing the right physical topology allows a company toexpand its networked services without losing reliabilityand efficiency.

Star Topology

A star topology provides centralized control of thenetwork.

Extended Star


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Partial Mesh Full Mesh


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Static and Dynamic Routing


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Typically, both static and dynamic routes are employed inan enterprise network

Static routing addresses specific network needs Depending on the physical topology, a static route can be

used to control the traffic flow. Limiting traffic to a single point of entrance/exit creates a

stub network.


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Static routing provides forwarding services without theoverhead associated with most dynamic routingprotocols.

Static routing provides more security than dynamicrouting, because no routing updates are required.


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Configuring Static Route

Router(config)#ip route [network-address] [subnet mask][address of next hop OR exit interface]


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Summary route


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A floating static route has a higher administrative distance than theroute learned from a dynamic routing protocol.

For that reason, a floating static route does not display in the routingtable

To create a floating static route, add an administrative distance value

to the end of the ip route command: Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.9.1 200 .


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Default Route

The final default route, located on the border router, sends the trafficto the ISP.

This route identifies the last stop within the enterprise as theGateway of Last Resort for packets that cannot be matched.


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Distance Vector Routing Protocols

Dynamic routing protocols are classified into two major categories:distance vector protocols and link-state protocols.

Routers running distance vector routing protocols sharenetwork information with directly connected neighbors.

Distance vector protocols calculate the best route basedon the distance from a router to a network.

An example of a metric used is hop count, which is thenumber of routers, or hops, between the router and thedestination.


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Distance Vector Routing Protocols


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Routing Information Protocol (RIP)

RIPv1 does not send subnet mask information in its routing updates and,therefore, does not support VLSM and CIDR.

By default, RIPv1 broadcasts its routing updates to all connected routersevery 30 seconds.

RIPv1 does not support Discontigous network


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RIPv2 is a classless routing protocol that supports VLSM and CIDR. RIPv2 also has the ability to turn off automatic summarization of

routes.


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When a router starts up, each RIP-configured interface sends out arequest message.

RIP-enabled neighbors send a response message that includesknown network entries.


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By default, RIPv2 sends and receives only version 2 updates. By default, RIPv1 sends version 1 updates, but receives both

versions 1 and 2.

So RIPv1 and v2 are not compatible so.next slide.


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Compatibility with RIP v1

NewYork

interface fastethernet0/0

ip address 192.168.50.129 255.255.255.192

ip rip send version 1

ip rip receive version 1


ip address 172.25.150.193 255.255.255.240

ip rip send version 1 2


ip address 172.25.150.225 225.255.255.240

router rip

version 2

network 172.25.0.0

network 192.168.50.0

Interface FastEthernet0/0 isconfigured to send and receiveRIP v1 updates.

FastEthernet0/1 is configuredto send both version 1 and 2updates.

FastEthernet0/2 has no specialconfiguration and thereforesends and receives version 2by default.

RIPv2

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Activity


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Configuring RIPv2

The basic RIP configuration consists of three commands: Router(config)#router rip

Enables the routing protocol

Router(config)#version 2

Specifies the version

Router(config-router)#network [network address] Identify each directly connected network that should be

advertised by RIP


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Configuring RIPv2


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Authentication

Whatever the reason, it is good practice to authenticate routing information transmittedbetween routers.

RIPv2, EIGRP, OSPF, IS-IS, and BGP can be configured to authenticate routinginformation.

This practice ensures routers will only accept routing information from other routers thathave been configured with the same password or authentication information.

Note: Authentication does not encrypt the routing table.



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Configuring authentication

Router(config)#key chain Romeo

Router(config-keychain)#key 1

Router(config-keychain-key)#key-string Juliet

The password must be the same on both routers (Juliet), but the name of the key(Romeo) can be different.

Router(config)#interface fastethernet 0/0

Router(config-if)#ip rip authentication key-chain RomeoRouter(config-if)#ip rip authentication mode md5

If the command ip rip authentication mode md5 is not added, the interface will use thedefault clear text authentication. Although clear text authentication may be necessary tocommunicate with some RIP v2 implementations, for security concerns use the moresecure MD5 authentication whenever possible.



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RIPv2 redistribution

Planning Redistribution

Locate the boundary router between two routing processes. Determine which routing process is the core or backbone

process

Determine which routing process is the edge or migrationprocess

Select a method for injecting the required edge protocol routesinto the core.

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Configuring Redistribution into RIP

Use this command to redistribute routes into RIP: Router(config-router)# redistribute protocol[process-id]

[match route-type] [metric metric-value] [route-map map-tag]

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RtrA(config)# router rip

RtrA(config-router)# redistribute ospf ?

Process ID

RtrA(config-router)# redistribute ospf 1 ?

match Redistribution of OSPF routes

metric Metric for redistributed routes

route-map Route map reference

Default metric is infinity.


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The redistribute command parameters for RIP

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Parameter Description

protocol Source protocol from which routes are being redistributed.

process-idThis value is an AS number. For OSPF, this value is an OSPFprocess ID.

match route-type

(Optional) Command parameter used for redistributing OSPFroutes into another routing protocol. For OSPF, the criterion bywhich OSPF routes are redistributed into other routingdomains.

metric metric-value

(Optional) Parameter used to specify the RIP seed metric forthe redistributed route. When you are redistributing into RIP,this value is not specified and no value is specified using the

default-metric router configuration command, then the defaultmetric is 0, which is interpreted as infinity, and routes will notbe redistributed. The metric for RIP is the hop count.

route-map map-tag(Optional) Identifier of a configured route map to beinterrogated to filter the importation of routes from this sourcerouting protocol to the current routing protocol.


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Problem with RIP

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Unlike RIPv1, with RIPv2 the automatic summarizationfeature can be disabled.

Router(config-router)#no auto-summary


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Problem with RIP

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qThe passive-interface command, issued in interface mode,disables routing updates on specified interfaces.

qRouter(config-router)#passive-interfaceinterface-type interface-

number


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Problem with RIP

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Routing Loop


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Problem with RIP

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Count to Infinity


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Problem with RIP

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Routing loops negatively affect network performance. RIPcontains several features designed to combat this impact.:

Poisoned reverse

Split horizon

Holddown timerTriggered updates


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Problem with RIP

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Split Horizon Split horizon dictates that a router receiving routing

information on an interface cannot send an updateabout that same network back out the sameinterface.


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Problem with RIP

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Holddown timerThe holddown timer refuses to accept route updates

with a higher metric to the same destinationnetwork for a period after a route goes down


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Verification and Troubleshooting Commands

There are several ways to verify and troubleshoot RIPv2. Many of the same commandsused for RIPv2 can be used to verify and troubleshoot other routing protocols.

It is always best to begin with the basics: 1. Make sure all of the links (interfaces) are up and operational.

2. Check the cabling.

3. Check to make sure you have the correct IP address and subnet mask on eachinterface.

4. Remove any unnecessary configuration commands that are no longer necessaryor have been replaced by other commands.



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Router#debug ip rip

RIP protocol debugging is on

Router#01:23:34: RIP: received v2 update from 192.168.4.22 on Serial1

01:23:34: 172.30.100.0/24 -> 0.0.0.0 in 1 hops

01:23:34: 172.30.110.0/24 -> 0.0.0.0 in 1 hops

Router#01:23:38: RIP: received v2 update from 192.168.4.26 on Serial0

01:23:38: 172.30.2.0/24 -> 0.0.0.0 in 1 hops

01:23:38: 172.30.1.0/24 -> 0.0.0.0 in 1 hops

Router#

01:24:31: RIP: sending v2 update to 224.0.0.9 via Ethernet0 (10.0.0.1)

01:24:31: 172.30.2.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 172.30.1.0/24 -> 0.0.0.0, metric 2, tag 001:24:31: 172.30.100.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 172.30.110.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 192.168.4.24/30 -> 0.0.0.0, metric 1, tag 0

01:24:31: 192.168.4.20/30 -> 0.0.0.0, metric 1, tag 0

Router(config)# line console 0

Router(config-line)# logging synchronous

multicast

Includes mask



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Router# show ip rip database172.19.0.0/16 auto-summary

172.19.64.0/24 directly connected, Ethernet0

172.19.65.0/24

[1] via 172.19.70.36, 00:00:17, Serial1

[2] via 172.19.67.38, 00:00:25, Serial0

172.19.67.0/24 directly connected, Serial0



172.19.86.0/24[1] via 172.19.67.38, 00:00:25, Serial0

[1] via 172.19.70.36, 00:00:17, Serial1

The show ip rip database command to check summary address entries in theRIP database.

These entries will appear in the database if there are only relevant child orspecific routes being summarized.

When the last child route for a summary address becomes invalid, thesummary address is also removed from the routing table.



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Common RIPv2 issues

The network statement does two things: It enables the routing protocol to send and receive updates on any local

interfaces that belong to that network.

It includes that network in its routing updates to its neighboring routers.



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Enhanced Interior Gateway Routing Protocol (EIGRP)

Cisco developed EIGRP as a proprietary distance vectorrouting protocol.


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The two main goals of EIGRP are to provide a loop-freerouting environment and rapid convergence. The metric used is a composite metric that primarily

considers bandwidth and delay.

The Diffusing Update Algorithm (DUAL) used by EIGRPguarantees loop-free operation while it calculates routes.


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EIGRP is a good choice for complex enterprise networksthat are composed primarily of Cisco routers. Its maximum hop count of 224 supports large networks. EIGRP does not send complete tables in its updates.

EIGRP multicasts partial updates about specific changes toonly those routers that need the information, not to allrouters in the area.

Instead of sending

periodic routing

updates, EIGRP

sends small hello

packets to maintain

knowledge of its

neighbors.


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Activity


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EIGRP Terminology and Tables

Neighbor table


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Neighbor tableThe neighbor table lists information about directly

connected neighbor routers.

If a hello packet is not received within the hold time, thetimer expires and DUAL recalculates the topology.


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Topology Table The topology table lists all routes learned from each

EIGRP neighbor.

The Diffusing Update Algorithm (DUAL) is used to prevent looping: Successor.

Feasible Distance (FD).

Feasible Successor (FS).

Reported Distance (RD) or Advertised Distance (AD).

Feasible Condition or Feasibility Condition (FC).


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DUAL Concepts

Successor is a neighboring

router that is usedfor packetforwarding and is

the least-costroute to thedestinationnetwork.

Feasible distance The lowest

calculated metricalong a path to adestinationnetwork.


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Reported distance (RD) The metric that a router reports to a neighbor about its own cost to

that network.

The reported distance or advertised distance is simply an EIGRPneighbor's feasible distanceto the same destination network.

Feasibility Condition (FC) Met when a neighbors RD is less than the local routers FD to the

same destination network.

DUAL Concepts


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Routing table The routing table displays only the best paths called thesuccessor routes.

EIGRP displays information about routes in two ways:The routing table designates routes learned through

EIGRP with a D.

EIGRP tags dynamic or static routes learned from otherrouting protocols or from outside the EIGRP network asD EX or external, because they did not originate from

EIGRP routers within the same AS.


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Routing table R3s Routing table


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Activity


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EIGRP Neighbors and Adjacencies

Before EIGRP can exchange packets between routers, itmust first discover its neighbors. EIGRP routers use hello packets to discover neighbors

and establish adjacencies with neighbor routers.

By default, hello packets are multicast every 5 seconds onlinks greater than a T1 and every 60 seconds on T1 orslower links.

On IP networks, the multicast address is 224.0.0.10. The hello packet contains information about the router

interfaces and the interface addresses. The hold time is the period that EIGRP waits to receive a

hello packet.


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The hold time is three times the duration of the hellointerval. When the hold time expires and EIGRP declares the route

as down, DUAL re-evaluates the topology and refreshesthe routing table.


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When a neighbor adjacency is established, EIGRP usesvarious types of packets to exchange and update routingtable information.


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Step 1

Step 2


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Step 3

Step 4


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Step 5

Step 6

Step 7


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Activity

EIGRP M i d C


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EIGRP Metrics and Convergence

EIGRP uses a composite metric value to determine the best path to adestination.

Bandwidth

Delay

Reliability

Load

Maximum Transmission Unit (MTU) is another value included in routingupdates, but is not a routing metric.

EIGRP M t i d C


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EIGRP Composite Metric & the K Values

EIGRP uses the following values in its composite metric Bandwidth, delay, reliability, and load.

The composite metric used by EIGRP: Formula used hasvalues K1K5.

K1 & K3 = 1.

All other K values = 0.

EIGRP M t i d C


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Use the show ip protocols command to verify the K values


EIGRP M t i d C


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Use the showinterfaces command toview metrics

EIGRP Metrics BandwidthEIGRP

uses a static bandwidthto calculate metric.

Most serial interfacesuse a default bandwidthvalue of 1.544Mbps (T1).

Modifying the bandwidth

value does not changethe actual bandwidth ofthe link.

EIGRP Metrics and Con ergence


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Delay

Delay is the defined as themeasure of time it takesfor a packet to traverse aroute

It is a static value

based on link type towhich interface isconnected.


EIGRP Metric Calculation


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Reliability (not a default EIGRP metric) A measure of the likelihood that a link will fail.

Measure dynamically & expressed as a fraction of 255 the higher thefraction the better the reliability.

Load (not a default EIGRP metric) A number that reflects how much traffic is using a link.

Number is determined dynamically and is expressed as a fraction of 255.

The lower the fraction the less the load on the link because it indicates lessload on the link.

EIGRP Metric Calculation


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The EIGRP topology table uses metrics to maintain values for feasible distance(FD) and advertised distance (AD) , or reported distance (RD).



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Activity



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Activity



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Activity

Configuring EIGRP


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Configuring EIGRP

Configuring EIGRP


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Configuring EIGRP

Add eigrp log-neighbor-changes

command to view changes in

neighbor adjacencies. This

feature helps the administrator

monitor the stability of the

EIGRP network.

Configuring EIGRP


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Configuring EIGRP

EIGRP authentication requires the use of a pre-shared key.

Configuring EIGRP


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Configuring EIGRP

EIGRP Route Summarization


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Like RIP, EIGRP automatically summarizessubnetted networks on the classfulboundary.

EIGRP installs a Null0 summary route in therouting table for each parent route.

The Null0 interface indicates that this is notan actual path, but a summary for

advertising purposes. Use the no auto-summary command to

disable the default summarization.



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Manual summarization provides a more precise control of EIGRP routes. A manually summarized route appears in the routing table as an EIGRP route

sourced from a logical, not physical, interface:

D 192.168.0.0/22 is a summary, Null0

Verifying EIGRP Operation


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y g p



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y g p

debug eigrppacket

displays

transmissionand receipt of

all EIGRP

packets


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y g p


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Summary


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y

Static route Dynamic routing RIP version 1 & 2

EIGRP protocol


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ccna dis3 - chapter 5 - routing with a distance vector protocol_ppt [compatibility mode]

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