Network mode: the server --- SW--- FW (NAT) --- public network
Configuration description: in the FW configure NAT SERVER to make NAT transition for the server service under the SW (because the server different service for the different port).
Fault phenomenon: the server cannot PING pass the public network address.
Check the FW configuration, find the following configuration:
nat server protocol udp global 188.8.131.52 40002 inside 192.168.1.4 40002
Check the FW SESSION TABLE and find that:
The port provided by the server is 3475, not 40002. So when the FW is in the matching, can't match to the 40002, so using the 63088 port to make the transition, thus become fault.
Change the port in the NAT SERVER configuration to be 3475, problem solved.
When FW use NAT SERVER command to make NAT transition, it is strictly according to the port number in the configuration command to make matching and transition. If NAT SERVER the port number in the configuration command is not consistent to the port actual server application, so when the FW received the message, only can matching the source IP and destination IP, can’t matching the port number, then random change a port to make NAT transition.
When configure NAT SERVER command, need to know exactly the port provided by the server end, so as to ensure the NAT translation successful.