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MPLS over GRE tunnels

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MPLS over GRE tunnels

Postby Guest » Sun Oct 25, 2009 8:43 am

Hello everybody,

I need some help in configuring MPLS over GRE tunnels. I did not find any proper configuration example to help me. I need to do this for encrypt the traffic between two PE routers. I have 7609 routers.





Re:MPLS over GRE tunnels

Postby Guest » Sun Oct 25, 2009 9:27 am


The same configurations of regular IP over GRE should be applied over physical interfaces, once the tunnel get ip, establish your routing protocol and LDP over the tunnel interface, based on the MPLS application you gone use decied the maximum number of labels will be included in one packet (4 bytes per label) then add the 24 GRE header and adjust your MTU.

Best Regards,

Mounir Mohamed


Re:MPLS over GRE tunnels

Postby Guest » Sun Oct 25, 2009 10:08 am

I understand. But, I really don't know how can I configure. I tray something but it isn't working.

I cannot establish the MP-BGP session over my GRE tunnel. I made the GRE tunnel and I put the GRE interface into one VRF.

I'm a little bit lost and I need a configuration example to have a starting point.


Alexandru Nitulescu


Re:MPLS over GRE tunnels

Postby Guest » Sun Oct 25, 2009 10:25 am

Hello alexandru,

one thing is to have a GRE tunnel as a VRF access link, another different matter is to use the GRE tunnel as your backbone link between PE routers.

in a few words to support MPLS forwarding and signaling you enable MPLS into the tunnel interface with mpls ip command.



interface tunnel 12

tunnel source <local PE pub ip address>

tunnel destination < remote PE pub ip address  >

ip address 10.x.y.1

mpls ip

! some mtu fixing may be necessary

interface loop5

ip address

an IGP running over 10.x.y.0/30 + mpls ldp router-id loop5 or change mpls source on the tunnel

router ospf 12

network 10.x.y.0 area 0

network area 0


router bgp 12

address-family vpnv4

neighbor activate

neighbor update-source loop5

neigh send-community both


the public ip addresses are different from 10.x.y.0/30 and 172.16.12.x and must be known / advertised

public ip addresses mustn't be advertised over IGP running over GRE tunnel (try and see what happens ...)

hope to help



Re:MPLS over GRE tunnels

Postby Guest » Sun Oct 25, 2009 10:27 am

Thanks a log for helping me. I will try to configure in the way you suggest next week to see what's happen'.



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