Cisco 2821 1841 BGP EIGRP MPLS questions

[Adam Hudson]

Currently all of our sites are connected through the mpls, as shown in the first network diagram. We just got fiber put in between SiteA and SiteB. What I need to do is disconnect SiteB from the MPLS, connect B to A through the fiber line as shown in the second diagram.  Basically the network will be B--Fiber-->A--MPLS-->C (SiteB and SiteC won’t be directly connected and that’s fine. As you can see from the diagram the link A-C on the MPLS runs BGP, but I want the link B-A to run EIGRP (simply because I see no reason to run BGP over it).

At this point, we have the fiber line up and connected to the routers, they can ping each other. What I specifically need help with is getting the EIGRP in order to run over that fiber line. I attached the configs for Site A and Site B. Can you help me?

[Adam Hudson]

A colleague suggested I need to use bgp backdoor command to lower the value of EIGRP so I can use it in this situation:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml#bgpbackdoor

Anyone have experience with this scenario?

[subramaniyakarthic]

Do you know if there is a need to increase the eBGP AD value. The backdoor is mainly used when you have two links - one a IGP and another circuit over eBGP connecting two sites and you want to prefer the IGP route.

Normally, eBGP routes would be preferred as it has AD-20. So we'll have to understand if there is a need for the backdoor command?  Have you tested the routes whether they are taking the expected path?

-K

[Adam Hudson]

karthic, at this point I'm just trying to put the above scenario in place. The more I look into the backdoor command the more I think I'm not going to need it because SiteC will only have one path to SiteB, that's through SiteA. But, I'm not sure exactly how to get the networks on SiteB, learned by SiteA over EIGRP, propogated to SiteC. Should that be happening already as I have a redistribute bgp command in my EIGRP on SiteA?

[cadet alain]

Hi,

yes  I think all is needed is mutual redistribution between BGP and EIGRP and nothing else special.

Regards.

Alain.

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[Giuseppe Larosa]

Hello Adam,

once the Site B routes are learned in EIGRP on Site A MPLS router all you need is:

a) under router bgp you can just add network commands for Site B routes (this approach works for N. routes < 200)

router bgp 65000

network SiteB-IPprefix1 mask SiteB-IPPrefix1-mask

...

network SiteB-IPprefixN mask  SiteB-IPPrefixN-mask

if the number of routes is great you may need to use redistribution of EIGRP into BGP

router bgp 65000

redistribute eigrp 100 route-map EIGRP-INTO-BGP

b) on Site A MPLS router you need to redistribute BGP into EIGRP

router eigrp 100

redistribute bgp 65000 route-map FROM-MPLS

default-metric 10000 1000 255 1 1500

Setting a seed metric using EIGRP metric components is mandatory for successful redistribution into EIGRP

Hope to help

Giuseppe

[Alessio Andreoli]

i would not take away BGP between your PEs....

and then why EIGRP? you can do cool stuff with OSPF as PE-CE routing protocol...

For the rest iam with Giuseppe's comments

Alessio