load-balancing over LDP-links

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Feb 20th, 2009
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Hi,


I was wondering if it were possible to load-balance over P-router to PE-router LDP-links.

ISIS is used as IGP for announcing the PE routers' loopback ip addresses used for imBGP.



At first glance I wanted to set up a portchannel but the algoritms use mac/ip while here we are working with labels.

As a result we have most likely no decent loadbalancing because all traffic flows from 1 P-router to a single PE-router so the hashing will always select the same link of the channel.


Later on I started thinking creating a same-cost ISIS route to the PE loopback ip via an additional link between these 2 routers.

I would enable LDP on this additonal link as well.If all would work well we obtain load-balancing for VRF-traffic because

the P-router would have 2 labels for reaching the same PE loopback ip.


But then PHP appears in the picture and hence my question: would this LDP-loadbalancing between penultimate P-rtr and PE-rtr actually work?

The most important direction is from the P-router ro the PE-router.



Thanks in advance,


Dirk


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Giuseppe Larosa Fri, 02/20/2009 - 06:19
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Hello Dirk,


>> I would enable LDP on this additonal link as well.If all would work well we obtain load-balancing for VRF-traffic because

the P-router would have 2 labels for reaching the same PE loopback ip.


the load balancing should be based on inner service label and so iif multiple VPN labels and/or VRFs on the final PE you should get some load-balancing.


There was an interesting thread about this some mounths ago.

You can also put VRF traffic in an MPLS TE tunnel if load balancing results are not enough good.


see


http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Service%20Providers&topic=MPLS&topicID=.ee8558c&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40^1%40%40.2cc21d1d/4#selected_message



see the post by Harold Ritter where explains how the VC label is used to perform load-balacing decisions.


Hope to help

Giuseppe


d.versavel Fri, 02/20/2009 - 06:59
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Hi Giuseppe,


I will test it first in a lab environment next week and I wil keep you posted on the progress. Thanks for the URL that's going to be some lecture for the weekend.


Your assistance is greatly appreciated,


Kind Rgds,


Dirk Versavel

Belgium

Laurent Aubert Fri, 02/20/2009 - 19:47
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Hi,


For L3VPN traffic, the P routers will use IP source and destination addresses of the packet to calculate its hash value even if the lookup is based on the IGP label.


The VC label is used for L2VPN because it's a non-IP packet.


HTH


Laurent.

d.versavel Mon, 02/23/2009 - 00:38
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Hi Laurent,


thanks for your valuable feedback I will keep you posted on this one.


Thanks a lot and best rgds,


Dirk

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