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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