No Split Horizon with DMVPN & EIGRP

[Matthew Needs]

Hi All,

We look after many networks using DMVPN & EIGRP. They are very effective and are working well. I have a question with regards to

no ip split horizon

I know that you have to configure this command to allow routing updates between spokes via the hub's tunnel interface much like frame relay point to multipoint interfaces.. However, why doesnt this cause count-to-infinity? Im guessing its some kind of safety mechanism? Why doesnt the spoke router see it's local network advertised back via the hub?

Thanks guys

Matt

[bunce.jake]

Hi Matthew,

Nice question. I think it would be due to poison reverse. The following link may help:

https://learningnetwork.cisco.com/message/63897

Regards,

Jake

[Matthew Needs]

Thanks Jake... However, didnt we have this conversation a few hours ago? AS YOU'RE SAT RIGHT NEXT TO ME!!!!... ;o). Ha Ha. However,  I hope this helps the rest of the community? Confirmation would be nice if anyone can help out?

[west33637 · Accepted solution]

If you enable

no ip split-horizon

the hub will advertise the networks back out to the spoke, but the spoke will drop the advertisement because it will be receiving an advertisement from a neighbor with its own IP address as the

next-hop