Thursday, 5 July 2012

EIGRP: Summarization using Leak-map

EIGRP: Summarization using Leak-map
·         EIGRP does auto-summarization by default
·         You can disable this feature by adding “no auto-summarization” command under eigrp routing process.
·         When you do manual summarization, and still you want to advertise some specific routes to the neighbor, you can do that using leak-map.

Let me take a small topology to configure this:

R1----------------R2-------------------R3

·         R1, R2, R3: AS 100
·         R1 has 5 loopbacks:
·         1.1.1.1/32
·         1.1.1.2/32
·         1.1.1.3/32
·         1.1.1.4/32
·         1.1.1.5/32

Configs:

R1#show run | begin router eigrp 100
router eigrp 100
 network 1.1.1.1 0.0.0.0
 network 1.1.1.2 0.0.0.0
 network 1.1.1.3 0.0.0.0
 network 1.1.1.4 0.0.0.0
 network 1.1.1.5 0.0.0.0
 network 100.1.12.1 0.0.0.0
 no auto-summary
 eigrp router-id 1.1.1.1
!
R2#show run | begin router eigrp 100
router eigrp 100
 network 100.1.12.2 0.0.0.0
 network 100.1.23.2 0.0.0.0
 no auto-summary
 eigrp router-id 2.2.2.2
!
R3#show run | begin router eigrp 100
router eigrp 100
 network 100.1.23.3 0.0.0.0
 no auto-summary
 eigrp router-id 3.3.3.3
!
R1#show ip route eigrp
     100.0.0.0/24 is subnetted, 2 subnets
D       100.1.23.0 [90/2681856] via 100.1.12.2, 00:03:18, Serial1/0
R1#
R2#show ip route eigrp
     1.0.0.0/32 is subnetted, 5 subnets
D       1.1.1.1 [90/2297856] via 100.1.12.1, 00:02:30, Serial1/0
D       1.1.1.3 [90/2297856] via 100.1.12.1, 00:02:30, Serial1/0
D       1.1.1.2 [90/2297856] via 100.1.12.1, 00:02:30, Serial1/0
D       1.1.1.5 [90/2297856] via 100.1.12.1, 00:02:30, Serial1/0
D       1.1.1.4 [90/2297856] via 100.1.12.1, 00:02:30, Serial1/0
R2#

R3#show ip route eigrp
     1.0.0.0/32 is subnetted, 5 subnets
D       1.1.1.1 [90/2809856] via 100.1.23.2, 00:02:42, Serial1/1
D       1.1.1.3 [90/2809856] via 100.1.23.2, 00:02:42, Serial1/1
D       1.1.1.2 [90/2809856] via 100.1.23.2, 00:02:42, Serial1/1
D       1.1.1.5 [90/2809856] via 100.1.23.2, 00:02:42, Serial1/1
D       1.1.1.4 [90/2809856] via 100.1.23.2, 00:02:42, Serial1/1
     100.0.0.0/24 is subnetted, 2 subnets
D       100.1.12.0 [90/2681856] via 100.1.23.2, 00:03:50, Serial1/1
R3#

Observations:

·         Auto-summarization is disabled.
·         Manual summarization is not configured yet.

Configuring summarization in R2, towards R3:

R2(config-router)#int ser1/1
R2(config-if)#ip summary-address eigrp 100 1.1.1.0 255.255.255.248
R2(config-if)#
*Jul  5 14:37:27.143: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 100.1.23.3 (Serial1/1) is resync: summary configured
R2(config-if)#

R2#show ip route eigrp
     1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
D       1.1.1.1/32 [90/2297856] via 100.1.12.1, 00:05:41, Serial1/0
D       1.1.1.0/29 is a summary, 00:01:07, Null0
D       1.1.1.3/32 [90/2297856] via 100.1.12.1, 00:05:41, Serial1/0
D       1.1.1.2/32 [90/2297856] via 100.1.12.1, 00:05:41, Serial1/0
D       1.1.1.5/32 [90/2297856] via 100.1.12.1, 00:05:41, Serial1/0
D       1.1.1.4/32 [90/2297856] via 100.1.12.1, 00:05:41, Serial1/0
R2#

R3#
*Jul  5 14:37:25.703: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 100.1.23.2 (Serial1/1) is resync: peer graceful-restart
R3#
R3#show ip route eigrp
     1.0.0.0/29 is subnetted, 1 subnets
D       1.1.1.0 [90/2809856] via 100.1.23.2, 00:00:11, Serial1/1
     100.0.0.0/24 is subnetted, 2 subnets
D       100.1.12.0 [90/2681856] via 100.1.23.2, 00:05:53, Serial1/1
R3#

Observation:

·         Summarization is configured in R2
·         R3 is receiving the summarized route

·         Now, R3 wants to receive 1.1.1.1/32 along with the summarized route.
·         Let me configure leak-map in R2 to leak the route 1.1.1.3/32 to R3

R2(config)#ip prefix-list LEAK permit 1.1.1.1/32
R2(config)#
R2(config)#route-map LEAK-MAP
R2(config-route-map)#match ip address prefix-list LEAK
R2(config-route-map)#int ser1/1
R2(config-if)#ip summary-address eigrp 100 1.1.1.0 255.255.255.248 leak-map LEAK-MAP
R2(config-if)#
*Jul  5 14:54:08.327: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 100.1.23.3 (Serial1/1) is resync: summary configured
R2(config-if)#
R3#
*Jul  5 14:54:06.895: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 100.1.23.2 (Serial1/1) is resync: peer graceful-restart
R3#
R3#show ip route eigrp
     1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D       1.1.1.1/32 [90/2809856] via 100.1.23.2, 00:03:08, Serial1/1
D       1.1.1.0/29 [90/2809856] via 100.1.23.2, 00:19:49, Serial1/1
     100.0.0.0/24 is subnetted, 2 subnets
D       100.1.12.0 [90/2681856] via 100.1.23.2, 00:25:31, Serial1/1
R3#

Observations:

·         Now, R3 has 1.1.1.1/32 prefix.

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