4.EIGRP overview

BSCI v3.0—2-1 Configuring EIGRP Introducing EIGRP... • Flexible network design • Multicast and unicast instead of broadcast address • Manual summarization at any point • 100% loop-fre

BSCI v3.0—2-1

Configuring EIGRP

Introducing EIGRP

• Flexible network design

• Multicast and unicast instead of broadcast address

• Manual summarization at any point

• 100% loop-free classless routing

• Easy configuration for WANs and LANs

• Load balancing across equal- and unequal-cost pathways

• Advanced distance vector

EIGRP Key Technologies

• Neighbor discovery/recovery

– Uses hello packets between neighbors

• Reliable Transport Protocol (RTP)

– Guaranteed, ordered delivery of EIGRP packets to all neighbors

• DUAL finite-state machine

– Selects lowest-cost, loop free, paths to each destination

• Protocol-dependent modules (PDMs)

– EIGRP supports IP, AppleTalk, and Novell NetWare

– Each protocol has its own EIGRP module and operates independently of any of the others that may be running

EIGRP Neighbor Table

DUAL Terminology

• Selects lowest-cost, loop-free paths to each destination

• AD = cost between the next-hop router and the destination

• FD = cost from local router = AD of next-hop router + cost between the local router and the next-hop router

• Lowest-cost = lowest FD

• (Current) successor = next-hop router with lowest-cost, loop free path

• Feasible successor = backup router with loop-free path (AD

of feasible successor must be less than FD of current

successor route)

EIGRP Topology Table

EIGRP IP Routing Table

Router C Tables:

EIGRP Packets

• Hello: Establish neighbor relationships

• Update: Send routing updates

• Query: Ask neighbors about routing information

• Reply: Respond to query about routing information

• ACK: Acknowledge a reliable packet

Initial Route Discovery

EIGRP Metric Calculation

• By default, EIGRP metric:

Metric = bandwidth (slowest link) + delay (sum of delays)

• Delay = sum of the delays in the path, in tens of microseconds,

A  B  C  D Least bandwidth 64 kbps Total delay 6,000

A  X  Y  Z  D Least bandwidth 256 kbps Total delay 8,000

• Delay is the sum of all the delays of the links along the paths:

Delay = [delay in tens of microseconds] x 256

• Bandwidth is the lowest bandwidth of the links along the paths:

Bandwidth = [10,000,000 / (bandwidth in kbps)] x 256

EIGRP Metrics Calculation Example

router eigrp autonomous-system-number

• Defines EIGRP as the IP routing protocol

• All routers in the internetwork that must exchange EIGRP

routing updates must have the same autonomous system

number

Configuring EIGRP

network network-number [wildcard-mask]

• Identifies attached networks participating in EIGRP

• The wildcard-mask is an inverse mask used to determine how to

interpret the address The mask has wildcard bits, where 0 is a match and 1 is “don’t care.”

Router(config)#

Router(config-router)#

Network 192.168.1.0 is not configured on router A, because it is not directly connected to router A

Configuring EIGRP for IP

Using the Wildcard Mask in EIGRP

Using and Configuring the ip network Command for EIGRP

default-Example EIGRP Configuration

Verifying EIGRP: show ip eigrp neighbors

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#

Verifying EIGRP: show ip route eigrp

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, 00:05:07, 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

Verifying EIGRP: show ip protocols

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

Routing Information Sources:

Gateway Distance Last Update

Verifying EIGRP: show ip eigrp interfaces

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

Verifying EIGRP: show ip eigrp topology

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 -

Verifying EIGRP: show ip eigrp traffic

R1#show ip eigrp traffic

IP-EIGRP Traffic Statistics for AS 100

EIGRP Load Balancing

• Routes with a metric equal to the minimum metric are installed in the routing table (equal-cost load balancing)

• There can be up to six entries in the routing table for the same destination:

– The number of entries is configurable

– The default is four

– Set to 1 to disable load balancing

EIGRP Unequal-Cost Load Balancing

variance multiplier

• Allows the router to include routes with a metric smaller than the

multiplier value times the minimum metric route to that destination

Router(config-router)#

• Router E chooses router C to get to network Z, because it has

EIGRP Unicast Neighbor

• Setting a neighbor with the command to enable a unicast neighbor relationship:

Verifying EIGRP Unicast Neighbor

R1#show ip eigrp neighbors

IP-EIGRP neighbors for process 100

H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num

0 192.168.12.2 Se0/0/0 10 00:06:00 9 200 0 3

R2#show ip eigrp neighbors

IP-EIGRP neighbors for process 100

H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num

0 192.168.12.1 Se0/0/0 10 00:06:05 1284 5000 0 3

Using Passive-interface command with EIGRP

• EIGRP announces the directly connected network of an

Using Passive-interface command with EIGRP (Cont.)

• No need to talk to host by EIGRP

• Disables EIGRP on all interfaces by default

• Enables EIGRP only on selected interfaces