PPP no keepalives

| Thursday, March 25th, 2010 | No Comments »

While playing with my simulated serial WAN link. I thought I could simulate the link going down by turning off keepalives on one of the serial interfaces. After waiting 5, 10 minutes and still being able to ping across, I decided to turn off the other keepalive coming from the other switch!

Low and behold, the link was still active! Why?

Well apparently with HDLC encapsulation, this method would WORK! But not with PPP. First HDLC is a cisco proprietary protocol. So turning off the keepalives on just one side of the link would indeed turn off your link. It would actually cause your interface to flap as the other side is trying to get the link back up.

With PPP, it does NOT use the cisco keepalives. It uses LCP (Link Control Protocol) as it’s form of “keepalive”. I have yet to discover if there are any commands to turn this off. There is no such thing as “no PPP LCP” although that would be pretty cool.

If anyone has any ideas, please comment!

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