EIGRP summarization don't works

[AllertGen]

Hello everyone.

I have a lot of branches with a lot of small networks (around 14 networks at each branch):

C       10.0.0.112/28 is directly connected, FastEthernet0/0.7
C       10.0.0.96/29 is directly connected, FastEthernet0/0.2
C       10.0.0.80/28 is directly connected, FastEthernet0/0.11
C       10.0.0.64/28 is directly connected, FastEthernet0/0.4
C       10.0.0.56/29 is directly connected, FastEthernet0/0.21
C       10.0.0.48/29 is directly connected, FastEthernet0/0.8
C       10.0.0.32/28 is directly connected, FastEthernet0/0.51
C       10.0.0.24/29 is directly connected, FastEthernet0/0.20
C       10.0.0.16/29 is directly connected, FastEthernet0/0.16
C       10.0.0.8/29 is directly connected, FastEthernet0/0.5
C       10.0.0.4/30 is directly connected, FastEthernet0/0.3
C       10.0.0.0/30 is directly connected, FastEthernet0/0.15
C       10.0.0.192/26 is directly connected, FastEthernet0/0.50
C       10.0.0.128/26 is directly connected, FastEthernet0/0.17

So I want to use route summarization to send 1 route insteand of 14. After using command "ip summary-address eigrp" at the interface I see that branch router create a summarization route:

D       10.0.0.0/24 is a summary, 15:26:01, Null0

The sceme of connection looks like this:

But the central router still gets routes from branch router like this:

D        10.0.0.0/30 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.4/30 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.8/29 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.16/29 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.24/29 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.32/28 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.48/29 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.56/29 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.64/28 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.80/28 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.96/29 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.112/28 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.128/26 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1
D        10.0.0.192/26 [90/1286912] via 172.2.0.68, 12:30:09, Tunnel1

Configuration of EIGRP at the branch side:

interface Tunnel1
 ip summary-address eigrp 1 10.0.0.0 255.255.255.0 90

router eigrp 1
 passive-interface default
 no passive-interface Tunnel1
 network 10.0.0.0 0.0.255.255
 network 172.2.0.0 #Tunnel interface network
 no auto-summary
 eigrp stub connected

Configuration of EIGRP at central router:

interface Tunnel1
 no ip split-horizon eigrp 1

router eigrp 1
 passive-interface default
 no passive-interface Tunnel1
 network 172.2.0.0 #Tunnel interface network
 no auto-summary

Additional information: I'm using DmVPN (without spoke to spoke connections) for connection between the routers. Central router is 3925 (IOS c3900-universalk9-mz.SPA.152-4.M6a) and branch router is 2801 (IOS c2800nm-advsecurityk9-mz.151-4.M7).

Thanks in advance for any help.

Best Regards.

[Peter Paluch · Accepted solution]

Hello,

Your EIGRP stub routers (the branch routers) are currently configured with eigrp stub connected command. This command allows the stub router to advertise only directly connected networks. Even if address summarization is configured, the stub is not allowed to advertise the summary address.

The correction should be fairly simple: replace the eigrp stub connected command with eigrp stub connected summary on your branch routers. This should do the trick.

Please be aware that your EIGRP adjacencies may momentarily flap when you enter the eigrp stub connected summary - please accomodate the time of this change to a period of day where the connectivity outage of a couple of seconds is acceptable.

Best regards,
Peter

[AllertGen]

Hi, Peter Paluch.

It is so stupid of me but you are right. I really forgot about stub command and how it works (and it's really so stupid of me because I know well for what this command is).

Thanks you very much for a help.

Best Regards.

[Peter Paluch]

Hi,

Oh come on - don't blame yourself. I do not even try to count how many times I have missed a similar detail myself :)

Best regards,
Peter