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RE: Question on mpls vpls and ospf ECMP routes

  • From: "Dutta, Pranjal \(Pranjal\)" <pdutta@alcatel-lucent.com>
  • Date: Sat, 24 Feb 2007 20:54:38 +0530
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Hi,
        As the LDP session between rtr1 and rtr3 is targetted so, it doesn't matter what is the path hello messages should follow in either directions. LDP session should come up as long as birectional path exists between rt1 and rt3 for TCP connection and both path needn't follow the same route.

        Pseudowire (PW) setup is a demultiplexor exchanged by LDP between rtr1 and rtr3 and those labels are used to identify packets in a VPLS instance. PW is a bi-directional LSP. It is further ovelayed over your RSVP Tunnels across PSN network in both directions and the path followed by RSVP Tunnel between rt1->rt3 and rt3->rtr1 may vary. PW label is exchanged only between edge routers,rt1 and rt3, so it doesn't matter how the PW packets reach both the routers. Only matters that is reaches both ends via the RSVP Tunnels or other tunnels.

Hope this helps,

Pranjal


________________________________

From: sunil [mailto:sunilc@ipinfusion.com]
Sent: Sat 2/24/2007 7:29 AM
To: mpls-ops@mplsrc.com
Subject: [MPLS-OPS]: Question on mpls vpls and ospf ECMP routes



Hi

I have a question regarding mpls and ospf ECMP routes

 

I have the below topology

 

Rtr1--------------rtr2---------------rtr3

|                                         |

|                                         |

|---------------rtr4---------------------|

 

All the links have same cost.

I want to setup a VPLS from rtr1 to rtr3

So I configured ldp targeted peer from rtr1 to rtr3

And configured rsvp trunks from rtr1 to rt3 and rtr3 to rtr1

 

Since there are two routes from rtr1 to rtr3 with equal cost, 

rtr1 selects rtr1-rtr4-rtr3 route 

rtr3 selects rtr3-rtr2-rtr1 route

 

ldp send targeted hello messages through one route and rtr3 sends in different route.

So how the LDP targeted peer should behave? Should ldp session come up? 

And my rsvp trunks are taking different path and I am facing problem in making the vpls up.

 

What should be the expected behavior in the above case?

 

Thanks

Sunil


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