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IP Eigrp Summary address is not working

Hi all,

I have the below LAB created in GNS for the the eigrp summary address concept. But some how the eigrp summary address summarization is not forming for 192.168.64.0/21 network. Please help and let me know what mistake i have in the configuration.

Attached the lab diagram and the three router configuration.

Please find the sh ip route of R2 and R1

R2 Sh ip route : Able to see both the network has been summarized in R2 routing table.

 

R2#sh ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     1.0.0.0/24 is subnetted, 1 subnets
C       1.1.1.0 is directly connected, Serial1/0
     20.0.0.0/24 is subnetted, 1 subnets
C       20.20.20.0 is directly connected, FastEthernet0/0
C    172.1.0.0/16 is directly connected, Serial1/1
     172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
D       172.16.0.0/24 [90/2297856] via 172.1.1.2, 00:03:38, Serial1/1
D       172.16.0.0/22 is a summary, 00:03:38, Null0
D       172.16.1.0/24 [90/2297856] via 172.1.1.2, 00:03:38, Serial1/1
D       172.16.2.0/24 [90/2297856] via 172.1.1.2, 00:03:38, Serial1/1
D       172.16.3.0/24 [90/2297856] via 172.1.1.2, 00:03:38, Serial1/1
     172.25.0.0/24 is subnetted, 1 subnets
C       172.25.50.0 is directly connected, Loopback1
D    192.168.64.0/24 [90/2297856] via 172.1.1.2, 00:03:46, Serial1/1
D    192.168.65.0/24 [90/2297856] via 172.1.1.2, 00:03:47, Serial1/1
D    192.168.66.0/24 [90/2297856] via 172.1.1.2, 00:03:47, Serial1/1
     10.0.0.0/24 is subnetted, 1 subnets
D       10.10.10.0 [90/2172416] via 1.1.1.1, 00:06:22, Serial1/0
D    192.168.67.0/24 [90/2297856] via 172.1.1.2, 00:03:48, Serial1/1
D    192.168.1.0/24 [90/2297856] via 1.1.1.1, 00:06:23, Serial1/0
C    192.168.2.0/24 is directly connected, Loopback2
D    192.168.3.0/24 [90/2297856] via 172.1.1.2, 00:03:49, Serial1/1
     30.0.0.0/24 is subnetted, 1 subnets
D       30.30.30.0 [90/2172416] via 172.1.1.2, 00:03:50, Serial1/1
D    192.168.64.0/21 is a summary, 00:03:50, Null0
R2#

 

R1 Routing table : Then i am not getting the same in R1 for 192.168.64.0 Network:

 

R1#sh ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     1.0.0.0/30 is subnetted, 1 subnets
C       1.1.1.0 is directly connected, Serial1/0
     20.0.0.0/24 is subnetted, 1 subnets
D       20.20.20.0 [90/2172416] via 1.1.1.2, 00:15:00, Serial1/0
D    172.1.0.0/16 [90/2681856] via 1.1.1.2, 00:15:00, Serial1/0
     172.16.0.0/24 is subnetted, 4 subnets
D       172.16.0.0 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
D       172.16.1.0 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
D       172.16.2.0 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
D       172.16.3.0 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
     172.25.0.0/24 is subnetted, 1 subnets
D       172.25.50.0 [90/2297856] via 1.1.1.2, 00:15:00, Serial1/0
D    192.168.64.0/24 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
D    192.168.65.0/24 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
D    192.168.66.0/24 [90/2809856] via 1.1.1.2, 00:12:24, Serial1/0
     10.0.0.0/24 is subnetted, 1 subnets
C       10.10.10.0 is directly connected, FastEthernet0/0
D    192.168.67.0/24 [90/2809856] via 1.1.1.2, 00:12:25, Serial1/0
C    192.168.1.0/24 is directly connected, Loopback1
D    192.168.2.0/24 [90/2297856] via 1.1.1.2, 00:15:01, Serial1/0
D    192.168.3.0/24 [90/2809856] via 1.1.1.2, 00:12:25, Serial1/0
     30.0.0.0/24 is subnetted, 1 subnets
D       30.30.30.0 [90/2684416] via 1.1.1.2, 00:12:25, Serial1/0
R1#

Everyone's tags (1)
6 REPLIES
Cisco Employee

Hello,I believe you have

Hello,

I believe you have placed the ip summary-address eigrp command on a wrong interface of the R2 router. Currently, it is placed on S1/1 toward R3. If you want to see this summary address on R1, you need to to place this command on the S1/0 interface toward R1.

As a general rule, summarization placed on an interface affects routes advertised out that interface only. It will not cause the summary to be advertised out other interfaces on which it is not configured. This is exactly what you see here.

Best regards,
Peter

HelloAlso like to add also

Hello

Also like to add also the subnet should be set to a 22 bit mask- 192.168.64.0 255.255.252.0

res

Paul

 

Please don't forget to rate any posts that have been helpful. Thanks.

Hi Paul, Thanks for the reply

Hi Paul,

 

Thanks for the reply.

 

Just to make me more clear -- As a general rule, summarization placed on an interface affects routes advertised out that interface only. It will not cause the summary to be advertised out other interfaces on which it is not configured.------

 

I understood that the interface affects routes which is learned via the interface. In my case the R2 learned all the loopback address via S1/1 .. where i did summarization.... and also i am  doing the same in R1 S1/0 where it getting learned from R2. --- Please clarify !

 

Just to clarify .. also i understood the SNM difference ..i modified to a higher subnet just to make sure that is not causing any issue. ..Thanks for pointing that !!!!

 

Also is there any command to see the advertised and learned routes from the neighbours.

Regards,

Gan

Cisco Employee

Hello Gan,I understood that

Hello Gan,

I understood that the interface affects routes which is learned via the interface. In my case the R2 learned all the loopback address via S1/1 .. where i did summarization

This is not a correct understanding. Summarization is performed when routes are advertised out an interface, not when routes are learned via an interface. Learned routes will always be put into your routing table exactly as they were received. Only routes that you advertise yourself can be summarized in the moment they are sent out an interface.

Does this make sense?

Best regards,
Peter

 

Got it.... very happy now .

Got it.... very happy now ..that i learned a concept clearly... Thanks a ton !!!! 

Put the summary command under

Put the summary command under serial 1/0:

interface Serial1/0
 ip summary-address eigrp 1 192.168.64.0 255.255.248.0 5

HTH

kazim

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