L3 VPN CE routing

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Dec 21st, 2007
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How is CE configured for routing in a MPLS L3VPN in case there are overlapping addresses in different VPNs?Say I have two VRFs for companies A and B and their IP pools overlap...Since my CE needs to communicate to both A & B and is a member of both VPNs, how do i configure it to direct traffic to an IP say an overlapping pool present in both VPNs) to the appropriate VPN?

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royalblues Fri, 12/21/2007 - 06:07
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MPLS VPN makes use of Route-distinguisher to make customers prefix unique.

It is a 8 byte field that is added to the IPv4 prefix received from the customer. The result is a 12 byte VPN4 prefix which is unique.

For example, for a PE router to be able to distinguish between the IP address of one customer from the of another customer, we must add a unique route distinguisher to each



sumesh_un Sat, 12/22/2007 - 01:02
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thnks narayan

However how will the PE know to which VRF is the packet directed?Say the CE will have destination ip but this is an ip present in both VRFs on the PE?

CE is not VRF aware.

can it be achieved by source based routing at PE?

Nagendra Kumar ... Sun, 12/23/2007 - 06:54
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Hi Sumesh,

In PE, the interface which is connected to the CE will be configured with the respective VRF with the following command (this will associate the interface with the respective VRF instance)

"ip vrf forwarding "

Based on the VRF, the address lookup will be done and forwarded accordingly.

Below mentioned URL can help you to understand about basic MPLS VPN configuration.





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