[c-nsp] MPLS Load balancing Question

[Oliver Boehmer (oboehmer)]

Annu Roopa <> wrote on Thursday, June 15, 2006 11:22 AM:

>   The customer wants to do load balancing using the two PEs - PE1 and
> PE2. What i thought of is doing MHSRP on the CE such that some
> traffic goes over CE1 and some over CE2, such that both PE1 and PE2
> are used. But the challenge is the return trafffic may take a
> different PE while coming back in. This will cause an asymmetric
> traffic pattern and could be an issue for some apps like Voice.     

Asymmetric traffic should not be a major issue unless you run some
stateful firewalls close to CE1 and CE2. If you need symmetry, you can
advertise the prefixes differently into the vpnv4 clouds so remote
PE's/RR prefer one over the other (different med, local-pref, etc.). 

>   Question:
> 
>   Customer wants to do load balancing over PE1 and PE2 towards other
> PEs. Is this possible ? Is there any way we can have the return
> traffic use the same PE and yet have redundancy maintained. Any other
> gotchas to be aware of, other than loops between PE1 and Pe2 having
> same site.    

You need to use iBGP multi-path on the remote PE's so they import both
vpnv4 paths into their RIB and perform load-sharing across both PE1 and
PE2. If you have a RR in the MPLS cloud, you need to deploy different
RDs on the vrf on PE1 and PE2, otherwise the RR will only send a single
path to the remote PE's. Remote PE's will only use both paths if the IGP
costs from the remote PE to PE1 and PE2 are equal (you can enable eiBGP
multi-path on the remote-PE's to get around this).
 
	oli