routing loop when advertising specific subnet of another AS

[dfulguer]

I have this network setup:

remoteR0------- GRE/IPSec (eBGP) ----------- < HubR5 -----------CoreSW (iBGP/EIGRP) ------ HubR1 >--------- MPLS

I have networks in remoteR0 that I advertise via eBGP to HubR5.

HubR5 received it and redistribute it via EIGRP and CoreSW learned it.

HubR1 learned the route to remoteR0 via EIGRP from CoreSW.

To advertise the subnet on the MPLS cloud out via HubR1, I added the specific subnet on the network statement under BGP on HubR1

However, if I advertise the specific subnet, traceroute going back to remoteR0 shows a routing loop between HubR5 and CoreSW.

If I summarize the subnet of remoteR0 and advertise it to MPLS, traceroute going back to remoteR0 works fine. 

Is this a normal behavior or am I missing something.

Thanks.

[Harish Balakrishnan]

Hello,

R u doing a bgp to eigrp redistribution on hubr1 ? by any chance

Cheers

Harish.

Sent from Cisco Technical Support iPhone App

[dfulguer]

Yes, we have bgp to eigrp redistribution on hubr1

[Marwan ALshawi]

if you are redistributing BGP into EIGRP in tR1 then increase the metric

or exculde this route of R0 from being advertised back into EIGRP in R1

[dfulguer]

Thanks Marwan, Thanks Harish

not sure if we can do that.

the GRE/IPSec tunnel from remoteR0 to HubR5 is just a Backup connection

from RemoteR0, we have another router connected to the same MPLS cloud of HubR1

So from Hub site, we primarily learn the route via MPLS and need to redistribute to EIGRP the specific prefix learned

If the MPLS goes down from remoteR1, we will use the backup.

hubR5 ----------- GRE/IPSec (BU) --------- ----------- MPLS (Primary) -------------- hubR1

[Marwan ALshawi]

ok

then you can solve it using one of the ways bellow

- exclude this network form being advertised back from BGP to EIGRP in R1

- increase the metric of this route when being advertised from BGP to EIGRP

- advertise less spcific network as you did using summary route

this is just to make sure R5 will use the route path as R1 if its learn it over MPLS/eBGP then it will go the direct path and use the EIGRP if the that path is down

HTH

pls rate the helpful posts

[dfulguer]

hi marwanshawi, hi harish.

thanks again for your assistance.

Cheers!