At the risk of posting something on topic.. I have 2 routers (lets call them A and B), talking to different upstream providers, advertising 202.6.75.0/24 via BGP. 202.6.75.0/24 is subnetted, each subnet is on a different VLAN. These routers talk to each other with iBGP, giving each other everything (including 202.6.75.0/24 le 32). I run HSRP between the 2 routers. Router B prepends my ASN several times before advertising 202.6.75.0. Relevant stuff (on both boxes): router bgp 23729 network 202.6.75.0 no synchronization ! ip route 202.6.75.0 255.255.255.0 Null0 With this config, reachability for 202.6.75.0/24 hosts alternates on and off roughly every minute. 47% total loss over 10 minutes (ie 5 'bursts' of loss). These packets are all hitting my AS at router A. I've turned HSRP off and on again to see if that was causing problems (it wasn't). Several solutions I've found: - Turning the iBGP session to router B off. (uhh..) - Turning syncronization on. My understanding of BGP synchronization, is that BGP will only re-advertise with eBGP prefixes learned via iBGP after learning them via another IGP if one is running. <snip> ec-br-1(config-router)#do sh run | inc router router bgp 23729 bgp router-id 202.6.75.1 </snip> I'm not running any IGPs, so synchronization shouldn't be part of the equation. In any case, I'm not a transit provider. And, there seems to be no relation to readvertising routes here, the packets AFAICT are getting to router A and being dropped. I've got no problem running running with synchronization on at the moment, but thats not the point. :-) Any ideas/thoughts? -- Nathan Ward