cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
404
Views
0
Helpful
1
Replies

how LSP is established MPLS VPN

hichamlechqar
Level 1
Level 1

hey everybody

 i know that LSP without vpn MPLS   , is performed  like that :
CUST1 (10.10.10.1)  ---PE1 ----P ------P ----PE2 ----- CUST2 (20.20.20.2)
PE2 assigned a label (L1) to FEC 20.20.20.2 and sent at P this last receive (L1) and swap it to P with (L2) and the same thing  for PE1.
the P in this case without vpn MPLS know the CEF 20.20.20.2 in  LFIB table because it assigned label at 20.20.20.2 
my problem is that  in MPLS VPN the P not known CEF 20.20.20.2 (VRF A + label VPN) therefore how LSP is established in step when  PE2 add 2 label ,one for VPN and second label for which FEC ? it is 20.20.20.2 if yes the 20.20.20.2 is not known in RIB 
please some one explain me step to performed LSP in above case.
i have the same for 6PE (LSP for P )   

1 Reply 1

rais
Level 7
Level 7

For MPLS VPN network, usually all PEs know how to get to other PE routers via LSP tunnels. These are transport/outer tunnels/labels.

Over the transport tunnel, PE2 advertises to PE1 via BGP, to use a label L for 20.20.20.2. This L is inner label that is put on the packet leaving PE1, then PE1 also puts an outer/transport label on the packet as it exists out. All intermediate P routers just look at the transport/outer label to guide the packet all the way to PE2. PE2 knows what inner label is and guides the packet to correct interface for 20.20.20.2.

 

HTH.

 

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: