Routing

Hi

I have scenario like this. R1 is connected to R2 and R3 through IBGP peering. R2 and R3 are giving the same routes to R1. I want to load balance these routes on R1 to both R2 and R3. The IGP cost of R2 and R3 are un equal on R1.

I just want to know, on R1 if I put the multipath knob under IBGP peering group for R2 and R3 then multipath will ignore the IGP cost of R2 and R3 protocol next-hop?

Thanks

As I know BGP Multipath feature is applicable only on EBGP sessions therefore it won't work in your case.

Have you thought about Multi-Topology routing?

Using MT routing you can create a separate topology in IS-IS or OSPF and tune the link costs in order to achieve equall cost to iBGP peers.

Hi

Thanks for the reply. Could you please give me some link how to configure this multitopology routing OR is there any other thing I can look in to for this scenario?

Thanks

By the way in L3VPN VRF configuration on M/MX routers, there is the knob to ignore IGP cost with multipath for VPN rotues. This is "set routing-options multipath vpn-unequal-cost" But I am looking for the global table for IBGP routes how to ignore the IGP cost for protocol nexthop and use multipath to ignore the router-id/peer id and do the load balancing.

Any help would be appreciated. Thanks

There's a very elegant way to solve this problem using IGP Shortcuts, it's very flexible and easy although you'll have to create RSVP LSPs between iBGP peers:

http://www.juniper.net/techpubs/software/junos/junos91/swconfig-mpls-apps/igp-shortcuts.html#id-48866

After configuration of RSVP LSP and IGP shortcut option, you'll have to tune the RSVP LSP metric:

http://www.juniper.net/techpubs/software/junos/junos91/swconfig-mpls-apps/configuringa-static-lsp-metric.html

This way you'll achieve equal cost path to iBGP peers that won't affect in any way non BGP traffic.

Thanks