EIGRP poison reverse squashed and neighbor adyacency restart

[lazaro@unitronics.es]

Hi friends,

I've got two routers connected by port-channel where EIGRP is running. After a while, I can see the restart of the EIGRP adyacency and always the same sequence of events in one of the sides...

RLDAT001#sh ip eigrp event
Event information for AS 100:
1 08:10:59.956 Poison squashed: 10.8.0.0/16 reverse
2 08:10:59.956 Ignored route, dup routerid int: 10.254.5.1
3 08:10:59.956 Poison squashed: 10.254.5.1/32 reverse
4 08:10:59.956 Ignored route, dup routerid int: 10.254.5.1
5 08:10:59.880 Change queue emptied, entries: 111
6 08:10:59.880 Metric set: 172.16.5.160/28 metric(256537)
7 08:10:59.880 Update reason, delay: new if delay(Infinity)
8 08:10:59.880 Update sent, RD: 172.16.5.160/28 metric(Infinity)
9 08:10:59.880 Update reason, delay: metric chg delay(Infinity)
10 08:10:59.880 Update sent, RD: 172.16.5.160/28 metric(Infinity)
11 08:10:59.880 Route installed: 172.16.5.160/28 10.0.0.17
12 08:10:59.880 Route installing: 172.16.5.160/28 10.0.0.17
13 08:10:59.880 Find FS: 172.16.5.160/28 metric(Infinity)
14 08:10:59.880 Rcv update met/succmet: metric(256537) metric(256281)
15 08:10:59.880 Rcv update dest/nh: 172.16.5.160/28 10.0.0.17
16 08:10:59.880 Metric set: 172.16.5.160/28 metric(Infinity)
17 08:10:59.880 Metric set: 10.254.31.2/32 metric(131353)

...

This router EIGRP is configured like this...

router eigrp 100
network 10.0.0.16 0.0.0.3
network 10.8.0.0 0.0.255.255
network 10.9.0.0 0.0.255.255
network 10.10.10.64 0.0.0.3
network 10.10.10.68 0.0.0.3
network 10.254.5.0 0.0.0.255
network 192.168.5.0
network 192.168.8.0
neighbor 10.0.0.17 Port-channel100
passive-interface default
no passive-interface Port-channel100
eigrp router-id 10.254.5.1
!

interface Port-channel100
description RLDAM001
no switchport
ip address 10.0.0.18 255.255.255.252
ip pim sparse-mode
ip authentication mode eigrp 100 md5
ip authentication key-chain eigrp 100 EIGRP
ip hello-interval eigrp 100 1
ip hold-time eigrp 100 3
ip summary-address eigrp 100 10.8.0.0 255.255.0.0
end

Does anybody know what it is going on??

What is the exact meaning of "poison reverse squashed"? What are the events could trigger it??

Could this event make the EIGRP neighbor restart??

Thanks in advance.

Regards.

[marce1000]

                        Here are some info-resources on the subject

 Ref : https://www.ciscopress.com/articles/article.asp?p=27839&seqNum=9

 >...

 Poison squashed—The router threads a topology table entry as a poison in reply to an update (the router set up for poison reverse). While the router is building the packet that contains the poison reverse, the router realizes that it doesn't need to send it. For example, if the router receives a query for that route from the neighbor, it is currently threaded to poison.

 https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13681-eigrpfaq.html#poison

 M.

 M.

[lazaro@unitronics.es]

Thanks Marcel. These links are what I have found before the post, but I',m looking for deeper explanation. What are the triggers that make this event happens??

[Giuseppe Larosa]

Hello lazaro@unitronics.es ,

looking at the first lines of the log messages that you have provided we see:

1 08:10:59.956 Poison squashed: 10.8.0.0/16 reverse
2 08:10:59.956 Ignored route, dup routerid int: 10.254.5.1
3 08:10:59.956 Poison squashed: 10.254.5.1/32 reverse
4 08:10:59.956 Ignored route, dup routerid int: 10.254.5.1

In modern EIGRP implementation the EIGRP RID is reported in all types of routes ( in the past it was only for the external routes).

So at first sight the root cause may be a duplicated EIGRP router-id.

Check the configuration of both devices if you can. I see you have set manually the EIGRP router-id to 10.254.5.1 on the local node.

I would suggest to try to change it  to a different unused value.

Hope to help

Giuseppe

[lazaro@unitronics.es]

Thanks Giuseppe. I've checked and there are not duplicated RID. There must be something else.

Regards.