Explain why this happens and there's no solution please

[godzilla0]

Hello, we have a VPN concentrator at our side and then various VPN connections with Cisco's 871 routers. Once the costumer stops for lunch or something similar ( a lapse of time ) The VPN tunnel goes down and we have to do a ping to their network to bring the tunnel back. We tried everything and there's no apparent solution to this problem! We want the VPN always up no exception ! Can you say why and if you know, how to solve this issue ?

Thanks.

[JORGE RODRIGUEZ]

Xavier,

Try enabling isakmp keepalive at both ends.

e.i for router

router(config)#crypto isakmp keepalive 10

Have a look here

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

Rgds

Jorge