Hi,
My site is running multi-home bgp, with two different provider. Both line are ethernet connection to my two edge routers. As ethernet is a kind of 'always on' connection. if any problem with any ISP, such as the gateway down, the isp interface status is still up up in my edge router. How does bgp track the problem and failover to second isp automatically, any parameter ?
If the ISP is down then your BGP session will also drop out and so those routes will become invalid.
Chris.
If the ISP is down then your BGP session will also drop out and so those routes will become invalid.
Chris.
Sorry for the double post. It was stuck in the outbox :-(
BGP uses TCP as a transport so eventually the BGP session will timeout and the routes learned via that session will be yanked.
The keepalive and holdtime can be specified for each BGP neighbour:
neighbor [ip-address | peer-group-name] timers keepalive holdtime
Sets the keepalive and hold-time timers (in seconds) for the specified peer or peer group.
Actually, it doesn't depend on TCP killing the session. It also sends its own periodic KEEPALIVE messages; if it doesn't see these messages from the peer, it kills the session itself.
There is also the BGP external fast failover feature that can be enabled
Receive a default-route from each ISP and re-distribute. Then your clients will always have a valid route out. In my case I cross-connect the two edge routers with iBGP also to load-share the two connections.
alan
Have something to add? Share your thoughts — no account required.
Ask the community — no account required