BGP Routing Protocol Information: BGP Timers

CENIC has adjusted their BGP timers used on internal sessions and recommends setting these timers on our peering sessions with all Charter Associates and Associates. The timers we use are:

    Keepalives:  10 seconds 
    Hold Time: 30 seconds 

This means that it will take between 30 and 40 seconds for a session to drop, giving faster failure detection.

The Cisco default values that we are replacing are:

    Keepalives:  1 minute 
    Hold Time: 3 minutes

This means that by default, it can take up to four minutes on Ciscos for the session to fail before BGP can reconverge to backup paths.

Juniper default values are:

    Keepalives:  30 seconds 
    Hold Time: 90 seconds

Similarly with the above, it can take up to 120 seconds for the session to fail before reconvergence can occur.

The cost of this change is an increased risk of false failure detections, resulting in sessions dropping and routes flapping.