We have a problem with a site-to-site VPN tunnel between 2 Cisco ASA 5505's.
Cisco ASA has a public IP address on the outside interface provided by the datacenter ISP.
Cisco ASA connects to the internet via PPPoE via a DSL modem in bridge modem.
The ASA has a public IP on the outside interface.
Lately, the DSL line is not really steady. When the DSL line crashes, the customer resets the modem and the line comes up fine again. The modem is not the problem, it is already replaced.
However, while internet/DSL comes up fine, the site-to-site VPN does not. A tunnel is created, but the ASDM states that there are a lot of bytes TX, but to bytes RX. That means somehow the tunnel is set up but no traffic is received. The ASA on the other site reports the same.
When we manually logout the VPN tunnel via the ASDM, automatically a new tunnel is created by the ASA and from there on it works fine.
What could be the problem? We don't want to have to reset the VPN manually everytime the modem is reset.