The use of eBGP, iBGP, and EIGRP

[jmcgrady1]

I have a site which has two WAN links - each serviced by a Cisco ISR router. eBGP exists between each router and the ISR at the other end. Within the site network (including the routers) i have eigrp running.  Eigrp is redistributed into BGP, and vice versa.

My question is whether there is value in establishing iBGP between the two routers on site? Or would that be superfluous since eigrp is already running.

[pmckenzie]

Hi there

  if your question is "is it superfluous to run both EIGRP & IBGP"

then you would remember that the Admin distance of IBGP is 200 cf Admin dist of EIGRP 90

So only routes in routing table would be EIGRP.

If your question was "do I do away with EIGRP and replace with IBGP"

have a look at this discussion

https://community.cisco.com/t5/other-network-architecture/ibgp-vs-eigrp/td-p/3835706

hope this is usefule

Peter

[Richard Burts]

Perhaps I understand the question a bit differently than Peter, and so will answer the question in a different way. If an organization has 2 routers each running EBGP with a router at the other end, it is not considered superfluous to run IBGP between them. EIGRP may be running between them, and EIGRP might even carry all of the external routes that they learn. But EIGRP can not carry some of the BGP parameters that the routers need to have to effectively coordinate BGP routing. It is normally considered a Best Practice to run IBGP between the 2 routers that are running EBGP.