Module 2 Configuring EIGRP

Lesson 1 Introducing EIGRP

EIGRP capabilities and attributes: (Cisco proprietary protocol) � Fast convergence � Loop free � DUAL (Diffusing Update Algorithm) � VLSM & discontinuous subnetworks support � Partial updates – triggered updates � Multiple network-layer protocol support – IP, AppleTalk, Novel NetWare IPX � Seamless connectivity across all data link layer protocols and topologies � Sophisticated metric – 32 bit � Multicast & unicast – 224.0.0.10 EIGRP Key Technologies: � Neighbor discovery/recovery - hello � Reliable transport protocol (RTP) � DUAL finite-state machine � Protocol-dependent modules (PDMs) Neighbor Table: � List adjacent routers ( topology table –learned routes to each destination, feasible successor route routing table – best route to each destination, successor route best route – successor route feasible successor route – backup route to a destination, in topology table) � Neighbor’s adderss & interface � Neighbor -> hello (hold time) -> no response -> DUAL is informed of the

topology change DUAL � Select loest-cost, loop-free paths � AD (Advertised Distance) = cost <next-hop router - destination> � FD (Feasbible Distance) = cost <local - destination> = AD + cost <local –

netx-hop router> � Lowest-cost = lowest FD � (Current) successor – next-hop router with lowest-cost, loop-free path – lowest

FD � Feasible successor – backup router with loop-free path

(AD of feasible successor < FD of current successor route) � Default 4 successors can be added to the routing table. Max 6 Topology Table: � Contain all destinations advertised by neighboring routiers � Maintains the metric that each neighbor advettises for each destination (AD) &

the metric that this router would use to reach the destination via that neighbor (FD)

� Changed when a directly connected route or interface changes or when a neighobring router reports a change to a route

� Two states: active / passive � Active: the router is performing a recomputation � Passive: the router is not performing a recomputation (desired state) Routing Table: � The lowest FD – successor router EIGRP Packets: � Hello: neighbor discovery – multicasts, no acknowledgement requirement � Update: unicast to specific router or multicast to multiple router � Query: ask for feasible successor – multicast but can be retransmitted as unicast � Reply: unicast � ACK: for update, query and reply – unicast hello packets and contain a nonzero

acknowledge number

EIGRP Metric: (bandwidth & delay by default. 256 * IGRP metric) � Bandwidth: smallest bandwidth between source and destination � Delay: cumulative interface delay along the path � Reliability: worst reliability between source and destination, based on keepalives � Loading: worst load on a link between source and destination � MTU: (Maximum Transmission Unit) smallest MTU in the path EIGRP Metric Calculation: � Default : K1=K3=1, K2=K4=K5=0 � Default: Metric = bandwidth (slowest link)+ delay (sum of delay) � Metric = (K1*bandwidth) + [(K2*bandwidth)/(256-load)] + (K3*delay) � If K5 not equal to 0 Metric = Metric * [K5/(reliability + K4)] � Delay: sume of delay in the path, in 10ms, multiplied by 256 � Bandwidth = [10^7 / (minimum bandwidth link along the path, in kbps)] * 256 � K values are carried in EIGRP hello packets. Integrating the EIGRP & IGRP Routes � EIGRP: 32 bit; IGRP: 24 bit � EIGRP metric = IGRP metric * 256

Lesson 2 Implementing and Verifying EIGRP

Configuring Basic EIGRP: � R(config)#router eigrp autonomous-system-number � R(config-router)#network network-number [wildcard-mask] � R(config-if)#bandwidth kilobits (default T1)

NOTE: EIGRP automatically summarizes routes on the major netowork boundary EIGRP Default Route: � R(config)#ip default-network netowork-number

Verify EIGRP IP Routes and IP Operations: � R#show ip eigrp neighbors

� R#show ip router eigrp

R1#show ip eigrp neighbors

IP-EIGRP neighbors for process 100

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

0 192.168.1.102 Se0/0/1 10 00:07:22 10 2280 0 5

R1#

R1#show ip route eigrp

D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:07:01, Serial0/0/1

172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks

D 172.16.0.0/16 is a summary, 00:05:13, Null0

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

D 192.168.1.0/24 is a summary, 00:05:13, Null0

R1#show ip route

<output omitted>

Gateway of last resort is not set

D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:06:55, Serial0/0/1

172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks

D 172.16.0.0/16 is a summary, 00:05:07, Null0

C 172.16.1.0/24 is directly connected, FastEthernet0/0

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.96/27 is directly connected, Serial0/0/1

D 192.168.1.0/24 is a summary, 00:05:07, Null0

� R#show ip protocols

� R#show ip eigrp interface

R1#show ip protocols

Routing Protocol is "eigrp 100"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Default networks flagged in outgoing updates

Default networks accepted from incoming updates

EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0

EIGRP maximum hopcount 100

EIGRP maximum metric variance 1

Redistributing: eigrp 100

EIGRP NSF-aware route hold timer is 240s

<output omitted>

Maximum path: 4

Routing for Networks:

172.16.1.0/24

192.168.1.0

Routing Information Sources:

Gateway Distance Last Update

(this router) 90 00:09:38

Gateway Distance Last Update

192.168.1.102 90 00:09:40

Distance: internal 90 external 170

R1#show ip eigrp interfaces

IP-EIGRP interfaces for process 100

Xmit Queue Mean Pacing Time Multicast Pending

Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes

Fa0/0 0 0/0 0 0/10 0 0

Se0/0/1 1 0/0 10 10/380 424 0

� R#show ip eigrp topology

� R#show ip eigrp trafic

R1#show ip eigrp topology

IP-EIGRP Topology Table for AS(100)/ID(192.168.1.101)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

r - reply Status, s - sia Status

P 192.168.1.96/27, 1 successors, FD is 40512000

via Connected, Serial0/0/1

P 192.168.1.0/24, 1 successors, FD is 40512000

via Summary (40512000/0), Null0

P 172.16.0.0/16, 1 successors, FD is 28160

via Summary (28160/0), Null0

P 172.16.1.0/24, 1 successors, FD is 28160

via Connected, FastEthernet0/0

P 172.17.0.0/16, 1 successors, FD is 40514560

via 192.168.1.102 (40514560/28160), Serial0/0/1

R1#show ip eigrp traffic

IP-EIGRP Traffic Statistics for AS 100

Hellos sent/received: 429/192

Updates sent/received: 4/4

Queries sent/received: 1/0

Replies sent/received: 0/1

Acks sent/received: 4/3

Input queue high water mark 1, 0 drops

SIA-Queries sent/received: 0/0

SIA-Replies sent/received: 0/0

Hello Process ID: 113

PDM Process ID: 73

Lesson 3 Confirguring Advanced EIGRP Options

Automatic summarization: default - enable Manual summarization: � When the last specific route of summary goes away, the summary is deleted � Metric: minimum � Summary routes to interface null0 � R(config-router)#no auto-summary � R(config-if)#ip summary-address eigrp as-number address

mask [admin-distance]

Load Balancing Across Equal Paths: � Default – 4; Max – 6 (command: maximum-paths maximum-path) � maximum-path = 1 – disable load balancing � fast-switched – on a per-packet basis Load Balancing Across Unequal-Cost Paths: � R(config-router)#variance multiplie

� Two feasiblity conditions: 1. the loacl best metric (the current FD) > the best metric (AD) learned from the next router. 2. multiplie * the current FD > the metric throught the next route (alternative FD)

EIGRP Bandwidth Use Across WAN Links � Support : point-to-point links

Nonboradcast Multiacess (NBMA): point-to-point links Multipoint links

� Default - 50% bandwidth � command: bandwidth

ip bandwidth-percent eigrp as-number percent (percent can be greater than 100) Bandwidth Utilization over WAN Interfaces � Point-to-point subinterfaces using Frame Relay:

- T1 by default - manually configure bandwidth to match the contracted committed information rate (CIR) of the permanent virtual circuit (PVC). � Multipoint Frame Relay, ATM, ISDN PRI:

- all neighbors share the bandwidth equally - EIGRP uses the bandwidth on the physical interface divided by the number of neighbors on that interface to calculate the bandwidth attributed per neighbor � Each PVC can have a different CIR, creating an EIGRP packet-pacing problem � Multipoint intervace – convert these to point-to-point configuration or manually

configure bandwidth by multiplying the lowest CIR by the number of PVCs EIGRP WAN Configuration: � Frame Relay Hub-and-Spoke Topology

- configure each virtual Circuit as point-to-point, specify bandwidth = 1/10 of link capacity - increase EIGRP utilization to 50% of actual VC capacity

� Hybrid Multipoint - Configure lowest CIR vitual circuit as point-to-point, specify bandwidth = CIR - Configure higher CIR vitual circuits as multipoint, combine CIRS

Lesson 4 Confirguring EIGRP Authentication

Route Authentication � Simple password (plain-text): IS-IS, OSPF, RIPv2 � MD5: OSPF, RIPv2, BGP, EIGRP EIGRP MD5 Authentication � Router generates and checks every packet. Router authenticates the source of

each routing update packet that it receives. � Configure a key (password) and key ID on both the sending and the receiving

router; each participating neighbor must have same key configured. � Rotuer generates a message digest, or hash, of the key, key ID, and message � EIGRP allows keys to be managed using key chains � Specify key ID (number), key, and lifetime of key. (key activation times overlap

to avoid any period of time for which no key is activated.) � Fisrt valid actived key, in order of key numbers, is used Configuring MD5 Authentication � R(config-if)#ip authentication mode eigrp

autonomous-systme md5

� R(config-if)#ip authentication key-chain eigrp autonomous-systme name-of-chain

� R(config)#key chain name-of-chain � R(config-keychain)#key key-id � R(config-keychain-key)#key-string text � R(config-keychain-key)#accept-lifetime start-time

{infinite | end-time | duration seconds} � R(config-keychain-key)#send-lifetime start-time

{infinite | end-time | duration seconds} Troubleshooting MD5 Authentication � R#debug eigrp packets Example:

<output omitted>

key chain R1chain

key 1

key-string firstkey

accept-lifetime 04:00:00 Jan 1 2006 infinite

send-lifetime 04:00:00 Jan 1 2006 04:01:00 Jan 1 2006

key 2

key-string secondkey

accept-lifetime 04:00:00 Jan 1 2006 infinite

send-lifetime 04:00:00 Jan 1 2006 infinite

<output omitted>

interface FastEthernet0/0

ip address 172.16.1.1 255.255.255.0

!

interface Serial0/0/1

bandwidth 64

ip address 192.168.1.101 255.255.255.224

ip authentication mode eigrp 100 md5

ip authentication key-chain eigrp 100 R1chain

!

router eigrp 100

network 172.16.1.0 0.0.0.255

network 192.168.1.0

auto-summary

<output omitted>

key chain R2chain

key 1

key-string firstkey

accept-lifetime 04:00:00 Jan 1 2006 infinite

send-lifetime 04:00:00 Jan 1 2006 infinite

key 2

key-string secondkey

accept-lifetime 04:00:00 Jan 1 2006 infinite

send-lifetime 04:00:00 Jan 1 2006 infinite

<output omitted>

interface FastEthernet0/0

ip address 172.17.2.2 255.255.255.0

!

interface Serial0/0/1

bandwidth 64

ip address 192.168.1.102 255.255.255.224

ip authentication mode eigrp 100 md5

ip authentication key-chain eigrp 100 R2chain

!

router eigrp 100

network 172.17.2.0 0.0.0.255

network 192.168.1.0

auto-summary

Lesson 5 Using EIGRP in an Enterprise Network

Factors that Influence EIGRP Scalability � Quantity of routing information exchanged between neighbors; without proper

route summarization, this can be excessive � Number of routers that must be invlved when a topoloy change occurs � Depth of topology: the number of hops that information must travel to reach all

routers � Number of alternate paths rhrouth the network. (stuck in active (SIA)) EIGRP Query Process � Queries are sent when a route is lost and no feasible successor is available � The lost route is now in active state � Queries are sent to all neighboring routers on all interfaces except the interface to

the successor � If the neighbors do not have the lost-route information, queries aer sent to their

neighbors � If a router has an alternate route, it answers the qurey; this stops the query form

speading in that branch of the network EIGRP Stub � The EIGRP stub routing feature improves network stability, reduces resource

utilization, and simplifies remote router (spoke) configuration. � Stub routing is commonly used in a hub-and-spoke topology. � A stub router sends a special peer information packet to all neighboring routers to

report its status as a stub router. � A neighbor that receives a packet informing it of the stub status does not query

the stub router for any routes. Configuring EIGRP Stub � R(config-router)#eigrp stub [receive-only | connected |

static | summary] - receive-only: Prevent the stub from sending any type of route. - connected: Permits stub to send connected routes (may still need to redistribute) (command: redistribute connected). - static: Permits stub to send static routes (must still redistribute) (command: redistribute static). - summary: Permits stub to send summary routes. (command: ip summary-address or auto-summary) - Default - connected and summary

Limiting Updates and Queries: Using EIGRP Stub � R(config)#router eigrp 1 � R(config-router)#eigrp stub Example: eigrp stub Parameters � If stub connected is configured:

- B will advertise 10.1.2.0/24 to A. - B will not advertise 10.1.2.0/23, 10.1.3.0/23, or 10.1.4.0/24.

� If stub summary is configured: - B will advertise 10.1.2.0/23 to A. - B will not advertise 10.1.2.0/24, 10.1.3.0/24, or 10.1.4.0/24.

� If stub static is configured:

- B will advertise 10.1.4.0/24 to A. - B will not advertise 10.1.2.0/24, 10.1.2.0/23, or 10.1.3.0/24. � If stub receive-only is configured:

- B will not advertise anything to A, so A needs to have a static route to the networks behind B to reach them.

SIA Connections: (Stuck in Active) � The router has to get all replies form the neighbors with an outstanding query

before the router calculates the successor information � If any neighbor fails to reply to the query within 3 minutes by default, the route is

SIA, and the router resets the neighbor relationship with the neighbor that fails to reply.

Most Common Reasons for SIA Routes: � The router is too busy to answer the query – high CPU, membory problems � The link between the two routers is not good – some packets are lost � A failure causes traffic on a link to flow in only one direction – unidirectional link Preventing SIA Connections: Graceful Shutdown � Goodbye message is broadcast when an EIGRP ruting process is shut down, to

inform adjacent peers about the impending topology change.

� Before Router A resets relationship to router B when the normal active timer expires. However, the problem is the link between router B and C.

� After Router A sends an SIA-Query at half of the normal active timer. Router B acknowledges the query there by keeping the relationship up.