In fact using an loopback interface is kind of had a second hop, 1 of them is external the other is internal thru control-plane.
That's why need to use 2 hops if you had neighbors peering thru loopbacks Sent from my iPhone > On 26-02-2014, at 14:09, marc abel <[email protected]> wrote: > > Are you peering between loopbacks? In this case you would need to do > ttl-security hops 2. Your neighbor is going to decrement 1 ttl before > sending and then local router would decrement 1 before delivering to > loopback interface. This probably wouldn't show up in your traceroute, but > you would have a ttl of 253. > > > On Wed, Feb 26, 2014 at 10:22 AM, Christopher Lemish < > [email protected]> wrote: > >> Guys, >> >> I just turned up a BGP session for a customer (doing BGP Failover for >> them). I am using the "neigh ttl-security hops" cmd. A traceroute >> confirms it is 1 hop away. The Cisco documentation explains that if a TTL >> is received that equals the TTL value expected or is higher, the router >> will accept that packet. >> >> I was troubleshooting it quickly and the cmd "neigh x.x.x.x ttl-security >> hops 254" is the only hop count that maintains the BGP session. I thought >> I recall that the ttl-security cmd "must exactly" match the number of hops >> away from one of Joe's videos. But, I thought we could use the "neigh >> x.x.x.x ttl-security hops 1" which means it is 1 hop away and would accept >> a TTL of 254 or higher, indicating that it is 1 hop away. >> >> (TTL=255)-->(TTL=254) >> PE--------CE >> >> The IOS version of this 3925 is the following: >> Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version >> 15.2(4)M5, RELEASE SOFTWARE (fc2) >> >> Thank you, >> Chris >> >> _______________________________________________ >> Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: >> >> iPexpert on YouTube: www.youtube.com/ipexpertinc > > > > -- > Marc Abel > CCIE #35470 > (Routing and Switching) > _______________________________________________ > Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: > > iPexpert on YouTube: www.youtube.com/ipexpertinc _______________________________________________ Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: iPexpert on YouTube: www.youtube.com/ipexpertinc
