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Community Member

Cisco PPP Keepalives

Anybodies know how much the ppp keepalives packets siize (overhead) ? I need this value to find tune the ISDN dial backup...

My ISDN always takes more than 1 minutes to kick in the ISDN....when the remote LO is having line problem (Note: during the line fail, the local router still shown phys and line UP and it cause the backup interface to change state from standby to UP become slower)

Observation during testing:

The Cisco PPP Keep by default is set to 10 secs and will declare timeout once there are 3 consecutive of drop. By testing the above behavior, I wonder why it take 60 over secs only detect the lease line failure when I was manually shutdown other end router interface. Is it the keepalive will wait for another 10 secs for each its expected it will come back !! means 10 x 3 x 2ways = 60++ ? anybodies has document such as rfc to refers ?



Cisco Employee

Re: Cisco PPP Keepalives

I belive 5 keepalive needs to be missed consecutivly for line running PPP encapsultion before ios will disconnect the line.

So the line will be disconnected after 10x5=50 secs because of keepalive missed.

You can turn on

debug ppp packet

debug ppp error

to see and track keepalives

Following url fore more

Community Member

Re: Cisco PPP Keepalives

Thanks for your info but if I'm not wrong, the keepalives are supposely default to 3 consecutive to be missed for IOS before 12.2(8)T [ed]. The retires 5 only available or default for 12.2(13)T onwards.

By shorter the timeout or to faster the backup option using the dial backup, is it only can tweak the period (secs) paramters to address this issue ?

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