MPLS with iBGP

[cisco8887]

Hi Guys,

I have the following network setup

5 routers.

R1 and R5 are PE routers. R1 connection to R5 is R1->R2>R3>R4>R5

If I enable ospf I can then label switch from R1 to R5 but not using iBGP.

why ?

with iBGP I have full end to end connectivity between R1 and R5

Many thanks

[er.himanshukumaar1]

Hi Brother,

First why we use OSPF.

OSPF is use to reach loopback of R5 from all routers except R5(Loopback is directly connected) and same for R1.

since when iBGP is created the loopback ip of R5 from R1 is reachable and same for vice-versa.

Hence when routes are advertised via ibgp to R1 from R5 and vice-versa the next hop is the loopback ip of the originating router Which is R1 or R5. and according to next-hop( Route to next-hop) the labels assigned via LDP and also one factor is LDP has LSR ID which is loopback ip of that router (Default) hence these IPs (LSR ID) are also reachable. on these ip (LSR ID) our LDP packet will travel.

and remember in IBGP next-hop is not changed(except you make it RR or apply next-hop self)

Hence any IGP is run with MPLS and IBGP./MPBGP(VPNV4 family)

Thanks..

Himanshu Kumar

[cisco8887]

many thanks, I am not sure if I understood why ibgp does not work and ospf does reading your reply

can you please elaborate more