IPsec VPN has gone down, and will not come back up...

[echong481]

I'm no cisco genius, and the network engineer that setup our network is out on vacation... go figure...

anyway we are using IPsec VPN with a 3750 switch and a 2921 router at our headquarters.  Off site we are using 2911 routers. We've had no issues with our VPN until now... As far as i know no changes have been made to any of our network equipment to point to the VPN failure... the tunnels just went down abruptly and won't come back up.  I've tried restarting the routers/switches, to no avail.

any leads or help will be greatly appreciated.

[cashqoo]

there are many possible reasons and you may want to try the following:

1> no interesting traffic - you may need to send some traffic across to the remote site/s in order to establish the tunnels

2> try to check the syslogs if there is any information or errors.

3> run commands to verify the status, show crypto isakmp sa, show crypto ipsec sa

4> run debug commands, debug crypto isakmp, debug crypto ipsec

[echong481]

wellll... the vpn just decided it gave me enough of a heart attack and decided to come back up...

no idea why... any measures i can take to make sure this doesn't happen again?  Do the tunnels need traffic in specific intervals to maintain the connection?

[cashqoo]

vpn can be configured with keepalive.

http://www.cisco.com/en/US/products/ps6120/products_tech_note09186a00807e0aca.shtml#solution07

as for the counter measures, you may have to determine the root cause, possibly by checking the logs on both ends.

you can also check the configuration if they have been configured with keepalives.