Site-to-Site IPSEC VPN - connects but only way packets
We have found an issues with two ZyWALL 310's we are running. Both are on different leased lines/circuits and work fine, when you configure a VPN (even using the official setup guide) the VPN connects and you can see packets coming in one direction but we don't appear to get the response traffic.
The firewalls are running V4.33(AAAB.0) / 2019-01-09 09:40:42 and with a ping you can see the outbound increase on one and the inbound increase on the other firewall but no response is received. If you run the ping in the other direction nothing is logged on the firewall side.