MPLS-Layer-3-VPN Interview Questions-Part 1 || Scenario # 1

[@MIS0DIGITAL]

To establish the VRF it must use the physical interface, one interface per vrf. the loop back is use for ebgp as next hop self multibgp hop. ip address ipv4 between CE and PE1 then vpnv4 between PE1 and PE2. Penultimate hop pop is 2nd last router before PE egress LSR.

[@MIS0DIGITAL]

the question i want to ask is whether should RD and RT value be the same. If not why not ?

[@sivaraman8520]

Won’t work, because your P router is going to advertise label 3 (PHP) for the P-PE2 link to PE1. So if PE1 sends labeled VPN traffic, there is no Transport label, no P router has no reference of the VPN label and is going to black hole the traffic.

[@SivakumarNetLabs]

Thanks for the comment siva, let see how many comments coming for this question

[@networkengineer2734]

Can u explain why P router will advertise label 3 for the P-PE2 when we configure MP-ibgp through interface instead of loopback

[@Nash6688]

It will not work , PE1 will itself pop the label and do l3 lookup as it is PHP node and p1 is advertising a pop label for its directly connected intf which connects to p1 and pe2. Using loopback we are making sure pop happens on p1 and not on pe1

[@arunghosh5386]

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