OSPF load balancing

Unanswered Question
Aug 18th, 2009
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I want to do OSPF load balancing, but not working.

i have 3 sites, Site A, Site B, Site C.

All connected via mpls , and we running ospf with provider.

I want to load balance traffic on Site C, means customer sitting on site C, and one request should go to Site A and one should go to site B, per session.

now when i advertise subnet from Site A, and Site B , i only see advertisement from one site not both on site C.

one thing i noticed, when i advertise 10.10.10.x from site A, Site B also learn the same subnet being on same mpls cloud, doest it has any thing to do with it?

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Overall Rating: 5 (1 ratings)
Giuseppe Larosa Tue, 08/18/2009 - 04:08
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Hello Ahmad,

>> All connected via mpls , and we running ospf with provider

so this is a L3 MPLS VPN where OSPF is used as PE-CE protocol.

Be aware that on the service provider side OSPF is redistributed into multi protocol BGP so other factors can play a role in the choice that the PE node does on site C.

First of all a single BGP route is elected best and it is only this one to be redistributed into OSPF.

Second even if the PE node is able to install both BGP routes in the vrf routing table only one route is seen in OSPF because it is the result of redistribution of BGP vpnv4 routes into OSPF instance for your VRF.

In other words only the provider can see if multiple paths to net are available and used.

ask them to show you a sh ip route vrf vrf_name to see if both BGP paths are installed in their PE node.

Hope to help


ahmad82pkn Tue, 08/18/2009 - 04:38
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Very nice explanation giuslar.

Let me talk to provider.


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