EIGRP Route Advertisement

abbas.ali · ‎12-08-2009

I have a loopback internface 1.1.1.1 255.255.255.0 on R1 and advertising this route via EIGRP

R1

router eigrp 1

10.1.1.0 0.0.0.255

network 1.1.1.0 0.0.0.0

no auto-summary

R2

router eigrp 1

network 10.1.1.0 0.0.0.255

no auto-summary

obviously, I am learning route 1.1.1.0/24 on R2 via internal eigrp

These two router are connected via IPSEC tunnel and R2 should be able to learn netwok 1.1.1.0/24 only when the MPLS network is down.

R1 is also connected to Core Internal router via different EIGRP AS.

R1

router eigrp 56

network 172.16.1.0 0.0.0.255

redistribute eigrp 1 metric 10000 100 255 1 1500

no auto-summary

Core Router

router eigrp 56

redistribute eigrp 1 metric 10000 100 255 1 1500

network 172.16.1.0 0.0.0.255

How can I force network 1.1.1.0/24 to router 2 learned via Core Router that is connected to MPLS clould instead of R1. Rightnow, due to internal EIGRP 90 takes precedence over external EIGRP distance 170.

Any suggestions !

I tried offset-list on R1 that is advertising networ 1.1.1.0/24, but it didn't seem to work since changing the metric will not effect the Admin Distance in offset list.

Router 1

router eigrp 1

network 10.1.1.0 0.0.0.255

network 1.1.1.0 0.0.0.255

redistribute eigrp 56 metric 10000 100 255 1 1500

offset list 99 out 214425476 fastethernt 0/0

no auto-summary

access-list 99 permit 1.1.1.0 0.0.0.255

marpina · ‎12-08-2009

Can you try using this way to change the AD for external routes.

Router eirgp 1

distance eigrp 90 80

I hope this help you

Best regards

Marcelino

abbas.ali · ‎12-08-2009

Marcelino,

I tried changing the admin distance as well, but no luck. Running out of ideas here what to do.

vdadlaney · ‎12-08-2009

Hi, if i understood your scenario correctly one method would be to redistribute 1.1.1.1 into eigrp instead of putting a network statement for it on R1. You could than specify a higher metric for that route so when R1 advertises that route to R2 it would have a higher metric than the route that is being advertised by the Core to R2 hence R2 would prefer the route via the Core instead. Please advise if this solution works or if this was not what you were looking for. Thx

steve · ‎12-09-2009

Hi Ali,

On R2 matching routes for 1.1.1.0/24 will be added to the routing table based on Administrative Distance, so manipulating the metric (with offset lists or otherwise) will not help.

I know that you have already tried manipulating the AD but it might be worth double checking that the AD is being correctly changed. Try "debug ip routing" to see what is actually happening.

Also, if possible, try experimenting with different ways of chaning the AD. For example, if EIGRP AS 1 is only required for resilience, then you might want to change the AD for internal routes in EIGRP AS 1 on R2 to 200.

Finally, have a look at the EIGRP topology details - see below. As you will see, External Data is available for redistributed routes. This External Data will include the originating EIGRP AS (for routes redistributed between EIGRP ASs) and it may be that EIGRP will always prefer the originating AS - this is very much speculation but it is worth checking.

#show ip eigrp 1 topology 1.1.1.0

#show ip eigrp 56 topology 1.1.1.0

Cheers

Stephen

milan.kulik · ‎12-09-2009

Hi,

I agree with Steve.

I even think what Marcelino advised was correct, but should be applied on R2 eigrp process 56,

i.e.:

Router eirgp 56

distance eigrp 90 80

on router R2.

Best regards

Milan

vdadlaney · ‎12-09-2009

Hi All,

I still think that redistributing the network into eigrp with a higher metric (hence making it less preferred) will be the easiest solution as it would achieve the desired result. I would appreciate if someone could advise why that would not work as I might have misunderstood. Thx for your help.

vinodsharma7 · ‎12-10-2009

Hi,

I agree redistributing this network into eigrp with higher metric would solve the problem.. as when we redistribute this network its ad would be 170 similar to the routes learned from MPLS.

Thanks

steve · ‎12-10-2009

Hi Guys,

I agree, redistributing 1.1.1.0/24 should also set the AD 170 and then the route would be chosen on metric. However, I think you would need to redistribute connected (with a route-map matching 1.1.1.0/24) on both EIGRP 1 and EIGRP 56. I don't think this will work if you redistribute connected on EIGRP 1 and then redistribute EIGRP 1 to EIGRP 56.

Cheers

Stephen