Jump to content

TS B1 DMVPN Potential Bug or a Tricky T-shoot ??

Recommended Posts

Did anyone encounter these logs on R17,R18:


*May 9 17:31:15.553: %ADJ-5-PARENT: Midchain parent maintenance for IP midchain out of Tunnel0, addr - looped chain attempting to stack




Problem is that to establish tunnel, R17 need to reach NBMA IP of R15. Ideally R17 should go default route provided by R12. But, see below:



R17#show ip route

Routing entry for

Known via "eigrp 200", distance 170, metric 26905600, type external

Redistributing via eigrp 200

Last update from on Tunnel0, 00:00:01 ago

Routing Descriptor Blocks:

*, from, 00:00:01 ago, via Tunnel0

Route metric is 26905600, traffic share count is 1

Total delay is 51000 microseconds, minimum bandwidth is 100 Kbit

Reliability 255/255, minimum MTU 1476 bytes

Loading 15/255, Hops 1



To reach of R15 and to establish tunnel, R17 is using its route for learnt over the same tunnel and hence this error log.


In order to stop R15 from advertising its NBMA .10 IP, I removed "red connected" and tunnel came up.


After this we see no route for and it goes out via



R17#show ip route

% Subnet not in table




R17#show ip route

Routing entry for, supernet

Known via "static", distance 1, metric 0, candidate default path

Routing Descriptor Blocks:


Route metric is 0, traffic share count is 1



Not sure if there is any other way of doing it or not ?

Share this post

Link to post
Share on other sites

this log menas that u hava a recursive routing loop !

explanation : the correct way to run DMVPN is to have underlay and overlay saparate instances of routing protocols ....

so to reach nbma address u need to go via underlay and to reach VPN address u need to go overlay.


if for some reason the router sees that to reach underlay ip addresses he needts to go via the tunnel (overlay)....u are in truble and u got urself a loop.


the same thing happens in ur case ! underlay routes got into overlay protocol..... try to find where and filter it out.


hope this will give u a clear idia. =)

  • Like 1

Share this post

Link to post
Share on other sites

Midchain parent maintenance = NBMA problem (recurssive lookup)

NBMA Problem = tunnel src or dst being routed over tunnel.

Check redis con etc on Hub and Spokes.

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...