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New Member

EIGRP/Loop Problem

We have two connections into our Layer3 switches that connect to our WAN provider at two geographically separate sites. They are doing EIGRP with us then redistributing into BGP. There is a 90MB circuit that connects our two sites to each other aside from our WAN connections. Site A has a 30MB connection to our provider and Site B has a 1.5MB connection. Traffic leaving Site B to one of our offices on the WAN goes out the 1.5MB and back through the 30MB connection in Site A.

The problem I'm having is when one of our remote sites goes down we get a loop between Site A and Site B (see below). How do I prevent this loop in the future?

10.210.x.x is Site A Network

10.220.x.x is Site B Network

32.246.x.x is WAN Provider

SiteA#traceroute 10.106.10.202

Type escape sequence to abort.

Tracing the route to 10.106.10.202

1 10.210.31.77 4 msec 0 msec 0 msec

2 32.246.46.185 4 msec 8 msec 8 msec

3 32.246.46.170 28 msec 20 msec 24 msec

4 10.220.7.217 24 msec 24 msec 24 msec

5 10.220.7.214 24 msec 24 msec 24 msec

6 10.210.206.4 24 msec 24 msec 24 msec

7 10.210.248.33 24 msec 24 msec 24 msec

8 10.210.31.77 24 msec 24 msec 24 msec

9 32.246.46.185 28 msec 32 msec 28 msec

10 32.246.46.170 48 msec 44 msec 44 msec

11 10.220.7.217 48 msec 44 msec 48 msec

12 10.220.7.214 44 msec 48 msec 48 msec

13 10.210.206.4 48 msec 44 msec 44 msec

14 10.210.248.33 44 msec 44 msec 48 msec

15 10.210.31.77 44 msec 48 msec 44 msec

16 32.246.46.185 52 msec 52 msec 52 msec

17 32.246.46.170 68 msec 68 msec 68 msec

18 10.220.7.217 68 msec 68 msec 68 msec

19 10.220.7.214 64 msec 64 msec 68 msec

20 10.210.206.4 68 msec 68 msec 68 msec

21 10.210.248.33 68 msec 68 msec 68 msec

22 10.210.31.77 68 msec 68 msec 64 msec

23 32.246.46.185 72 msec 72 msec 76 msec

24 32.246.46.170 92 msec 92 msec 88 msec

25 10.220.7.217 88 msec 96 msec 88 msec

26 10.220.7.214 92 msec 92 msec 92 msec

27 10.210.206.4 100 msec 96 msec 96 msec

28 10.210.248.33 88 msec 96 msec 88 msec

29 10.210.31.77 88 msec 88 msec 96 msec

30 32.246.46.185 92 msec 100 msec 96 msec

6 REPLIES

Re: EIGRP/Loop Problem

Friend,

This is a classic mutual distribution problem. What you need to do is to filter the routes while redistribution.

Can you redistribute BGP into EIGRP and use only netowrk statements in BGP?

Narayan

New Member

Re: EIGRP/Loop Problem

Thanks for your help. I guess I can use BGP and redistribute into EIGRP. So I just put the networks in BGP and redistribute them into EIGRP on my switches running both EIGRP and BGP? I guess I'll have to coordinate this with my provider since they control the routers.

Can you explain to me why this is happening?

Re: EIGRP/Loop Problem

Post the configuration if you can for the routers. A simple network diagram would help too.

Narayan

New Member

Re: EIGRP/Loop Problem

Unfortunately I cannot get the router configs as they are managed by our provider. I've attached a simple diagram of the devices involved in the loop. Please let me know if you need more info.

Silver

Re: EIGRP/Loop Problem

Hi,

the best practice for a mutual redistribution is to tag your prefixes.

Please check this example:

router eigrp 77

redistribute ospf 17 metric 1544 2000 255 1 1500 route-map ospf-to-eigrp

...

!

router ospf 17

redistribute eigrp 77 metric 500000 subnets route-map eigrp-to-ospf

...

!

route-map ospf-to-eigrp deny 10

match tag 13

!

route-map ospf-to-eigrp permit 20

set tag 11

!

route-map eigrp-to-ospf deny 10

match tag 11

!

route-map eigrp-to-ospf permit 20

set tag 13

You have to do that on both routers, of course.

Remember: if no value is specified, the remote autonomous system number is used for routes from BGP and EGP; for other protocols, the default is 0.

For the BGP point of view, you can set a metric, or a community also. For example:

eigrp to BGP: set metric X or set community (but check with your ISP).

BGP to eigrp: match metric X or community, and deny it.

HTH

Andrea

Re: EIGRP/Loop Problem

Hi Andrea,

Nicely explained.

BR,

Mohammed Mahmoud.

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