EIGRP over an MPLS ISP link

[r.rios728]

Hello All....

Just want to have something clear about how EIGRP works.  Actually I have the following topology:

RouterA<------->(ISP MPLS Cloud)<------->RouterB

Router A WAN interface = 10.1.2.1/30

Router B WAN interface = 10.8.50.104/30

I'm trying to configure EIGRP between these routers.  As you can see, WAN interfaces are configured in different subnets because I'm using an ISP whom uses MPLS L3 VPNs.  I can reach each side without problems, but when I tried to configure EIGRP the neighbors are not coming UP.

EIGRP is configured:

Router A:

router eigrp 10

network 10.1.2.0 0.0.0.3

no auto-summary

Router B:

router eigrp 10

network 10.8.50.0 0.0.0.3

no auto-summary

As a temporary solution I create GRE tunnels so EIGRP neighbors are on the same subnet.  This way I have EIGRP working without problems, but I would prefer not using gRE tunels because of MTU issues in the future.

Thanks in advance for your help.

[Giuseppe Larosa]

Hello Ricardo,

being a L3 VPN service your only possible EIGRP neighbor is the PE router, so if the SP is willing to use EIGRP with you in both sites you can use it, otherwise you cannot as you have already seen in your tests.

Be aware that the SP may charge you additional fee for moving to EIGRP as PE-CE protocol or they can even deny this possibility because EIGRP is proprietary.

most common PE-CE protocol is eBGP, then OSPF.

Hope to help

Giuseppe

[r.rios728]

thanks four your answer...

I will have to keep the GRE tunnel working then

[Yasir Ashfaque]

You can Tweak the MTU to make it work, configure it as 1400, and TCP MSS as 1360.