BGP Multipath with Route Reflector

[taoufikbelmekki]

A great hello to everyone,

i'm trying to implement bgp equal cost multipath (maximum path) within an MPLS VPN network, but i'm issuing a problem with my RR and i'm not getting the expected results, because no BGP load balacing occurs.

i mentionned the RR because i did some research to figure out why it does not work and i found in some docs that RR kills the load-balancing.

is there any solution to implement such a feature in an MPLS VPN network with a Route Reflector ?

thanks in advance

[chintan-shah]

Hi,

This could due to fact that you are using same RD and RR will do best path selection and send only single path to PE.

If you use unique RD at least site which is multihomed to two PE , you will get both prefix to remote PE and will be able to use multipath feature.

Regards,

Chintan

[Mohamed Sobair]

Hello,

The reason is because when you have multipe IBGP paths installed in the routing table, the RR advertises only one single best path. To avoid this behaviour, all routers connected to the multihoming sites should have different Route Distinguisher RD per VRF basis.

Keep in mind is that this feature is designed per Vrf basis and its configured under the VRF address family.

Regards,

Mohamed

[shivjain]

Hi

In case of multihoming when the same CE routre is advertised by different PEs, RR first check the IGP cost to reach that PE, if the cost is equal then the route selection is done on the basis of smallest router id. So the load balancing and sharing is not possible.

But if you donot want to use different RD, in that case you split your subnet into multiple small ones and advertise them from different PEs. You will not get 50-50 load balancing but load sharing will work.

regards

Shivlu Jain