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New Contributor

Re: GRE tunnel flapping -

You are right -- the edge router this tunnel goes to is terminating 29 other BGP tunnels.  I only got full access to the router yesterday -- And when I said that end router to end router pings stay up even when the tunnel goes down - I have relied on others to tell me that -- and I think I got it right

The tunnel drops only last for 30 seconds -- never when we are watching --

I turned console logging to serial console port on and set it to verbose -- but it only sends banners and logins to my file --  There has to be a way that I have not found yet for this thing to tell me more

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New Contributor

Re: GRE tunnel flapping -

What are consequences of sending no keepalives?

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New Contributor

Re: GRE tunnel flapping -

I was unable to find what the tunnel # is on the Adtran

I did run debug bgp -- If I run it on the console port I get the results I have above -- they are consistently 15 sec apart

If I run from a telnet session I get

debug BGP

#

2015.09.03 11:12:34 BGP.KPA VRF: -DEFAULT- x.x.x.x[109]: Sending KeepAlive

2015.09.03 11:12:34 BGP.KPA VRF: -DEFAULT- x.x.x.x[109]: Transmitting msg, type=KEEPALIVE, len=19

2015.09.03 11:12:38 BGP.KPA VRF: -DEFAULT- x.x,x,x[109]: Received KeepAlive$

BGP.KPA VRF: -DEFAULT- x.x.x.x[109]: Sending KeepAlive

This circuit is delivered as 10Mb ethernet

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Contributor
Contributor

Re: GRE tunnel flapping -

Your GRE tunnel will stay up all the time, at least from a router interface point of view.  It will only go down if the source interface IP is removed from that source interface or if the source interface goes down (cable unplugged, admin shut).

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New Contributor

Re: GRE tunnel flapping -

so in this context, keepalives are more imnotdeads with the presumption that you are dead if I don't hear you x # of times in a row. That is interesting

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Contributor
Contributor

Re: GRE tunnel flapping -

Something like that, yes.  One main reason for it is so that the router can treat a GRE interface like a physical interface, and it will stop forwarding traffic over the interface because when it goes down, the GRE interfaces subnet is removed from the primary routing table as well as any routes pointing to an IP in that subnet.