BGP update will take IGP or RSVP/LDP

dwater2010

All,

When we have L3 VPN scenario for example:

CE1---PE1---P---PE2---CE2

We have RSVP LSP from PE1 to PE2 to reach the PE2 loopback IP.

Now when we do the show route <PE2 Loopback> we see the two path in routing table
one via the IGP (Pref of 10 in case of OSPF)
Other via RSVP (Pref of 7)

Now we have IBGP between the loopback of PE1 and PE2 so the question I have is will IBGP build on RSVP LSP or it will be via IGP. If it is via RSVP then make sense as it has low pref so it will be selected but if it is via IGP then I am little confuse in path selection, can someone help me with this?

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Comments

hoogen82

inet.0 table is what it will look at... I am assuming you did not put the Pe2 loopback as install in the mpls lsp... IGP is what it would use to form the IBGP connection

dwater2010

Thanks for reply so it means it will use inet.0 but inet.3 will be used for vpn routes to resolve bgp nexthop which might be LSP?

Aldur

dwater2010 wrote: »

Thanks for reply so it means it will use inet.0 but inet.3 will be used for vpn routes to resolve bgp nexthop which might be LSP?

well, inet.3 won't be used necessarly for BGP nexthop resolution, the IGP in inet.0 gets used for that. What happens is if a route is received by a IBGP speaker and the BGP protocol nexthop associated with that route is found in the inet.3 table, any traffic going to that route will take the LSP, be it RSVP or LDP.

Hopefully this makes sense, I've been up all night working and my thoughts are as congruent as they ought to be.

dwater2010

so it is something Router will prefer the LSP path to forward data and all control traffic will use inet.0. In case of VPN it has VPN label and need transport tunnel to carry VPN data to remote end.

Aldur

Yup, control plane traffic will use inet.0, and dataplane traffic can use, and will use if it's VPN dataplane traffic, inet.3.

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