On Thu, 26 Mar 2009 07:23:01 -0700 (PDT), Rob <>
wrote:
>On Mar 25, 10:17*pm, Andrey Tarasov <and...@email.com> wrote:
>> Rob wrote:
>> > On Mar 25, 3:21 pm, Andrey Tarasov <and...@email.com> wrote:
>> >> rcsdrob wrote:
>> >>> We have three core sites that are each connected via point-to-point
>> >>> DS3s, (triangle design) using OSPF. *We also have an MPLS DS3 using
>> >>> BGP going into each site as well. *One site is completely VoIP and
>> >>> requires QoS treatment. *We would like to load balance between the P2P
>> >>> and MPLS links at each site and allow for dynamic failover should a
>> >>> link or two fail. *Is this possible? *If so, how is it accomplished?
>> >>> My coworker is leaning toward GRE tunnels, but I would like other
>> >>> opinions and options before we dive headlong down this trail.
>> >> Lets see if I can guess your current situation correctly -
>> >> Your P2P links are preferred and MPLS is only used when both P2P links
>> >> at particular site have failed. Your MPLS is regular L3 VPN and not any
>> >> kind of L2TPv3/AToM/etc.
>> >> Are both P2P and MPLS terminated on the same router?
>> > Thanks for your response. *You are correct, the P2P links are
>> > preferred and the MPLS links are primarily used for failover, except
>> > for one site that is the VoIP gateway for 30 remote offices. *The MPLS
>> > links use L3 VPN access. *The P2P and MPLS connections terminate on
>> > different routers at each of the sites.
>>
>> I see two pretty big issues with this setup and your goal -
>>
>> First one is the fact that links have different capacity. While you can
>> get 45Mbps between pair of sites on P2P, MPLS DS3 is oversubscribed at
>> each site and as minimum at one location also carries remote traffic
>> (either VoIP only or with data). You can trick routers that it's equal
>> cost multipath, but in reality sessions sent over MPLS will be at
>> disadvantage.
>>
>> Second is different QoS policies - with MPLS one being quite inferior.
>> Depends on what you do you may get different traffic behavior between
>> P2P and MPLS.
>>
>> That being said, you may want to look into policy based routing. With
>> PBR you can ship specific (ideally non-interactive) traffic over MPLS.
>>
>> Regards,
>> Andrey.
>
>
>Andrey,
>Thank you for your suggestion. We have considered routing across the
>multiple links based on destination and type of traffic. We were
>hoping to make the most efficient use of the available bandwidth to
>all types of traffic, but it doesn't sound feasible with the disparate
>WAN links in use.
>
1 issue may be that routes leaked through MPLS are going to be
classified as OSPF external, and OSPF will prefer the internal routes.
What sometimes makes sense is to choose the route depending on
subsections of the address space - eg if subnet x/24 is at the remote
site, advertise x/25 via BGP as well as x/24
That way 50% of the target addresses prefer BGP when both routes are
up.
You can then tweak the routing to load balance by destination subnet -
it wont be as efficient as letting the router do session based
balancing.
But you can get some extra capacity out of your multiple paths at the
cost of manually sorting out the split in load.
>Thanks,
>Rob
--
Regards
- replace xyz with ntl
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