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Chapter 15 - Configuring EIGRP

Cisco & IP Addressing
Louis D. Rossi, Louis R. Rossi and Thomas Rossi
  Copyright © 1999 The McGraw-Hill Companies, Inc.

Chapter 15: Configuring EIGRP
Overview
Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary protocol. Cisco defines IGRP as an advanced distance-vector routing protocol.
EIGRP is a classless routing protocol, which means it does support VLSM.
Cisco also defines EIGRP as a hybrid routing protocol because it has characteristics of both distance-vector and link-state routing protocols. EIGRP will communicate with directly connected neighbors but NOT periodically; communication takes place only when a change occurs. As a result it is very quiet when compared to other distance-vector protocols.
EIGRP has several unique features, which may well be why Cisco calls it an advanced routing protocol.
Some of those features are:
  1. Scalability—EIGRP is not limited to 15 hops as is IP RIP.
  2. Event Triggered Updates—EIGRP sends updates when topology changes occur.
  3. Multiple paths—EIGRP has the ability to keep track of multiple routes that have an equal as well as an unequal metric.
  4. Sophisticated metric–EIGRP uses a combination of metrics to determine the best route:
  Bandwidth
  Delay
  Load
  Reliability
  Maximum Transmission Unit (MTU)
  5. EIGRP supports VLSM.
  6. Multiple Protocol Support—EIGRP supports IP, IPX, and Appletalk. This can be a very important feature if your organization is running more than one of these protocols, especially if they are running on your serial links. Take for instance IP RIP and IPX RIP running over serial links. The routing updates of IP RIP every 30 seconds and of IPX RIP every 60 seconds will eat up a significant portion of bandwidth.
EIGRP will reduce routing traffic significantly by using one protocol to update both the IP and the IPX routing tables.
Due to the fact that EIGRP is proprietary to Cisco, the router needs to be running the Cisco IOS. OSPF is a viable alternative.
Refer to Figure 15.1 and Table 15.1.
Figure 15.1  Four-Router EIGRP Topology
Table 15.1  Addresses Used with Figure 15.1
S0
S1
S2
E0
Router_A
10.10.8.9
N/A
N/A
10.10.1.1
Router_B
10.10.8.1
10.10.12.1
10.10.4.1
N/A
Router_C
10.10.12.9
N/A
N/A
10.10.2.1
Router_D
10.10.4.2
N/A
N/A
10.10.3.1
Mask
255.255.255.0
255.255.255.0
255.255.255.0
255.255.255.0
Configuration Commands
Router_B(config)#router eigrp 100
Router_B(config-router)#network 10.0.0.0
Figure 15.2  EIGRP Configuration Commands
Configuring EIGRP is very much the same as configuring IGRP, but what happens behind the scenes is very different.
Verifying Configuration
Router_B show run
Current configuration:
!
version 11.3
no service password-encryption
!
hostname Router_B
!
interface Serial0
  ip address 10.10.8.1 255.255.255.0
  no ip mroute-cache
  no fair-queue
!
interface Serial1
  ip address 10.10.12.1 255.255.255.0
!
interface Serial2
  ip address 10.10.4.1 255.255.255.0
!
interface Serial3
contined on next page
  no ip address
  shutdown
!
interface TokenRing0
  no ip address
  shutdown
!
interface BRI0
  no ip address
  shutdown
!
router eigrp 100
  network 10.0.0.0
!
router rip
  network 10.0.0.0
!
router igrp 100
  network 10.0.0.0
!
ip classless
!
line con 0
line aux 0
line vty 0 4
  login
end
Figure 15.3  The “show run” Command
Router_B#sh ip prot
Routing Protocol is "rip"
  Sending updates every 30 seconds, next due in 5 seconds
  Invalid after 180 seconds, hold down 180, flushed after 240
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Redistributing: rip
  Default version control: send version 1, receive any version
    Interface        Send  Recv   Key-chain
    Serial0          1     1 2
    Serial1          1     1 2
    Serial2          1     1 2
  Routing for Networks:
    10.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.8.9   120  00:00:09
    10.10.12.9  120  00:00:25
    10.10.4.2  120  00:00:22
  Distance: (default is 120)
Routing Protocol is "igrp 100"
  Sending updates every 90 seconds, next due in 16 seconds
  Invalid after 270 seconds, hold down 280, flushed after 630
  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
  IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  IGRP maximum hopcount 100
  IGRP maximum metric variance 1
  Redistributing: igrp 100, eigrp 100
  Routing for Networks:
    10.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.8.9  100  00:00:18
    10.10.12.9  100  00:00:13
    10.10.4.2  100  00:00:38
  Distance: (default is 100)
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: igrp 100, eigrp 100
  Automatic network summarization is in effect
  Routing for Networks:
    10.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.8.9       90            00:01:31
    10.10.12.9      90            00:01:31
    10.10.4.2       90            00:01:31
  Distance: internal 90 external 170
Figure 15.4  The “show ip protocol” Command
Viewing the Routing Table
Router_B#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
    D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
    N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
    E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
    i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
    U - per-user static route, o - ODR
Gateway of last resort is not set
  10.0.0.0/24 is subnetted, 6 subnets
D    10.10.1.0 [90/2195456] via 10.10.8.9, 00:03:39, Serial0
D    10.10.2.0 [90/2195456] via 10.10.12.9, 00:03:39, Serial1
D    10.10.3.0 [90/22798336] via 10.10.4.2, 00:03:39, Serial2
C    10.10.4.0 is directly connected, Serial2
C    10.10.8.0 is directly connected, Serial0
C    10.10.12.0 is directly connected, Serial1
Figure 15.5  The “show ip route” Command
Router_B has 3 directly connected networks and 3 routes that are discovered by the EIGRP process.
The default administrative distance of EIGRP is 90. Take note when viewing the configuration file that IP RIP and IGRP are still configured, yet all of our routes are discovered through EIGRP. The lower the administrative distance, the more reliable the routing protocol. Therefore the networks learned by the RIP and IGRP processes are ignored.
The metric for EIGRP is the result of a calculation that EIGRP performs. At this point, do not be concerned with the actual number; what is important to know is the lower the number the better the route.
Since EIGRP supports VLSM we should take a look at a VLSM addressing scheme.
In Figure 15.6 we will use the same network topology but with a new addressing scheme.
Figure 15.6  Four Router EIGRP Network Topology
Table 15.2  Addresses used with Figure 15.5
S0
S1
S2
E0
Router_A
172.16.0.10
N/A
N/A
10.10.1.1/24
Router_B
172.16.0.9
172.16.0.13
172.16.0.5
N/A
Router_C
172.16.0.14
N/A
N/A
10.10.3.33/28
Router_D
172.16.0.6
N/A
N/A
10.10.3.17/28
Mask
255.255.255.252
255.255.255.252
255.255.255.252
Notice we no longer have a contiguous network. The 172.16.0.0 network is in the middle of the 10.0.0.0 network. We are also using VLSM: the 10.0.0.0 network has two different masks 255.255.255.0 and 255.255.255.240.
Configuration Commands
EIGRP by default will perform auto summary; in other words, it will act as a classful routing protocol. The “no auto-summary” command (Figure 15.7) will force EIGRP into acting as a classless routing protocol.
Router_C(config)#int e0
Router_C(config-if)#ip address 10.10.3.33 255.255.255.240
Router_C(config-if)#int s0
Router_C(config-if)#ip address 172.16.0.14 255.255.255.252
Router_C(config-if)#router eigrp 100
Router_C(config-router)#network 10.0.0.0
Router_C(config-router)#network 172.16.0.0
Router_C(config-router)#no auto-summary
Figure 15.7  The “no auto-summary” Configuration
Verifying Configuration
Router_C#show run
Building configuration...
Current configuration:
!
version 11.2
no service password-encryption
no service udp-small-servers
no service tcp-small-servers
!
hostname Router_C
!
interface Ethernet0
  ip address 10.10.3.33 255.255.255.240
!
interface Ethernet1
  no ip address
  shutdown
!
interface Serial0
  ip address 172.16.0.14 255.255.255.252
  no fair-queue
  clockrate 56000
!
interface Serial1
  ip address 10.10.12.9 255.255.255.0
  shutdown
  clockrate 56000
!
router eigrp 100
  network 10.0.0.0
  network 172.16.0.0
  no auto-summary
!
router rip
  network 10.0.0.0
!
router igrp 100
  network 10.0.0.0
!
no ip classless
!
line con 0
line aux 0
line vty 0 4
  login
!
end
Figure 15.8  The “show run” Command
Router_C#sh ip prot
Routing Protocol is "rip"
  Sending updates every 30 seconds, next due in 0 seconds
  Invalid after 180 seconds, hold down 180, flushed after 240
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Redistributing: rip
  Default version control: send version 1, receive any version
    Interface        Send  Recv   Key-chain
    Ethernet0        1      1        2
    Serial1          1      1        2
  Routing for Networks:
    10.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.12.1           120      00:24:47
  Distance: (default is 120)
  Routing Protocol is "igrp 100"
  Sending updates every 90 seconds, next due in 3 seconds
  Invalid after 270 seconds, hold down 280, flushed after 630
  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
  IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  IGRP maximum hopcount 100
  IGRP maximum metric variance 1
  Redistributing: igrp 100, eigrp 100
  Routing for Networks:
    10.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.12.1         100          00:25:07
  Distance: (default is 100)
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: igrp 100, eigrp 100
  Automatic network summarization is not in effect
  Routing for Networks:
    10.0.0.0
    172.16.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    (this router)       5         00:16:51
    10.10.12.1         90         00:24:48
    172.16.0.13        90         00:08:44
  Distance: internal 90 external 170
Figure 15.9  The “show ip prot” Command
Table 15.3  Appletalk & IPX Addresses
Appletalk Zone
Appletalk Cable
IPX Network
Router_A
S0
one
100-100
1
E0
left
400-410
CAD
Router_B
S0
one
100-100
1
S1
two
200-200
2
S2
three
300-300
3
Router_C
S0
two
200-200
2
E0
right
500-510
DAD
Router_D
S0
three
300-300
3
E0
top
600-610
TOP
Viewing the Routing Table
Router_C#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
    D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
    N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
    E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
    i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
    U - per-user static route, o - ODR
Gateway of last resort is not set
  10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
D    10.10.1.0/24 [90/2707456] via 172.16.0.13, 00:10:06, Serial0
D    10.10.3.16/28 [90/23310336] via 172.16.0.13, 00:10:06, Serial0
C    10.10.3.32/28 is directly connected, Ethernet0
  172.16.0.0/30 is subnetted, 3 subnets
C    172.16.0.12 is directly connected, Serial0
D    172.16.0.8 [90/2681856] via 172.16.0.13, 00:10:06, Serial0
D    172.16.0.4 [90/23284736] via 172.16.0.13, 00:10:06, Serial0
Figure 15.10  The “show ip route” Command
All the subnets of network 10.0.0.0 are in bold.
For your information and to point out how powerful EIGRP can be, I have included a configuration of EIGRP that will route IPX and Appletalk (Figure 15.11).
IPX and Appletalk can be very chatty; EIGRP will route these protocols with a minimum amount of traffic.
Figure 15.11  EIGRP Routing IPX and Appletalk
Router_D#sh run
Building configuration...
Current configuration:
!
version 11.3
no service password-encryption
!
hostname Router_D
!
appletalk routing eigrp 500
appletalk route-redistribution
ipx routing 0010.7b15.bd41
!
interface Ethernet0/0
  no ip address
  appletalk cable-range 600-610 600.180
  appletalk zone top
  ipx network BAD
!
interface Serial0/0
  no ip address
  no ip mroute-cache
  appletalk cable-range 300-300 300.207
  appletalk zone three
  ipx network 3
  no fair-queue
  clockrate 56000
!
interface BRI0/0
  no ip address
  shutdown
!
interface TokenRing0/0
  no ip address
  shutdown
  ring-speed 16
!
interface FastEthernet1/0
  no ip address
  shutdown
!
ip classless
!
ipx router eigrp 100
  network 3
  network BAD
!
line con 0
line aux 0
line vty 0 4
  login
!
end
Figure 15.12  Router_D Configuration of EIGRP Routing IPX and Appletalk
Router_D#sh app route
Codes: R - RTMP derived, E - EIGRP derived, C - connected, A - AURP
    S - static  P - proxy
6 routes in internet
The first zone listed for each entry is its default (primary) zone.
R Net 100-100 [1/G] via 300.176, 1 sec, Serial0/0, zone one
R Net 200-200 [1/G] via 300.176, 1 sec, Serial0/0, zone two
C Net 300-300 directly connected, Serial0/0, zone three
R Net 400-410 [2/G] via 300.176, 1 sec, Serial0/0, zone left
R Net 500-510 [2/G] via 300.176, 1 sec, Serial0/0, zone right
C Net 600-610 directly connected, Ethernet0/0, zone top
Figure 15.13  Appletalk Routing Table of Router_D
Router_D#sh ipx route
Codes: C - Connected primary network, c - Connected secondary network
    S - Static, F - Floating static, L - Local (internal), W - IPXWAN
    R - RIP, E - EIGRP, N - NLSP, X - External, A – Aggregate
s - seconds, u - uses, U - Per-user static
6 Total IPX routes. Up to 1 parallel paths and 16 hops allowed.
No default route known.
C    3 (HDLC),  Se0/0
C    BAD (NOVELL-ETHER),  Et0/0
E    1 [2681856/0] via  3.00__07.7816.fe54, age 00:03:33,
                         1u, Se0/0
E    2 [2681856/0] via  3.0007.7816.fe54, age 00:03:34,
                         1u, Se0/0
E    CAD [2707456/0] via  3.0007.7816.fe54, age 00:03:34,
                         1u, Se0/0
E    DAD [2707456/0] via  3.0007.7816.fe54, age 00:03:34,
                         1u, Se0/0
Figure 15.14  IPX Routing Table of Router_D

 


 
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