VPN 4.x Client (IPSEC/UDP) can connect to an IOS router 12.4 and authenticate successfully but can't ping and telnet to devices.
This configuration was fully tested in a simulated environment and worked using actual ip addresses and devices to be deployed in production. The device was moved into production and now the VPN client cannot even contact the IOS VPN peer when using IPSEC/UDP, however they can connect and authenticate using only IPSEC but still cannot pass traffic.
I went back to the simulated environment and it works fine. I thought maybe MTU or NAT-T but can't seem to get it working.