HI Subodh,
Let us assume the network setup as:
PE1--P1--P2--P3--P4--PE2
Before we start, route-summarization is not recommended in the LSP path.
Assume, the LSP path is between PE1-PE2. If the route-summarization is done at the P4 means, P4 advertises the summarized route to P3 & to its upstream neighbors. However, PE2 advertises non-summarized route to P4.
In this case, P3 will see the route originated from the P4 (as summarised) and will do the Penultimate Hop Popping and deliver the Packet to P4 with VPN label only.
Since the P4 will have no knowledge on the Packets with VPN label, it will just ignore it.
In a normal scenario, the P4 has to do the Penultimate Hop Popping & deliver the packet to PE2. So, it is not recommended to go for route-summarization.
Refer Question:3 on the useful link below:
http://www.killtest.org/642-611.pdf
Hope i am Informative. Pls RATE if HELPS
Best Regards,
Guru Prasad R.