On 2009-01-29, Daniel Ouellet <dan...@presscom.net> wrote: > The reason I asked is because for example I was testing configuration > using loopback interface and when I reboot and I do not run bgpd I can > ping the loopback interface no problem, however if I reboot and bgpd run > I can still ping it, however it will time out regularly and sometime be > dead for as much as a minutes in worst case and go up/down and the bgp > sessions with the loopback interface will flap. Not always but sometime > it does. I just find out by luck I guess when I work doing constant > ping. if I stop bgpd, all goes normal and no lost packets what so ever, > if I restart bgpd, then sessions come up, can stay up for a long time no > problem, but ping time to time to the same loopback will fail and it > will happened that some bgp sessions will flap. I don't recall have seen > this on previous version of bgpd and the configuration stayed the same, > just upgrade to 4.4. It's been running for a few months, but I see rare > flaps and digging in it, that's what I found. > > So, I was curious as to if any loopback interface shouldn't be use with > bgpd, witch I am pretty darn sure it can be done like any other bgp router. > > If I configure the sessions with the interface itself, it's good, if I > configure sessions with the loopback, I could see time to time flap and > ping fail to the loopback interface.
I'm using a loopback address on lo1 on my routers, but I assign the loopback a /32 and distribute that into OSPF. I don't have a route covering the subnet holding those /32, and I "route add -reject default 127.0.0.1", so if they're withdrawn from OSPF the route to the address goes away. I'm explicitly using these addresses as router-id in both bgpd and ospfd, and of course running the BGP sessions to (neighbour address) and from (local-address) those addresses. A loopback on the local router shows up like this in bgpctl sh fib: ... flags: * = valid, B = BGP, C = Connected, S = Static N = BGP Nexthop reachable via this route r = reject route, b = blackhole route flags prio destination gateway * 4 195.95.187.1/32 195.95.187.1 ... and another router's loopback like this: ... * 32 195.95.187.3/32 195.95.187.243 (this is on -current; on 4.4 you won't have the priorities. prio 4 is connected, 32 is ospf, bgp would be 48).