Usg3040：public network exit，report server by public address，and configured default routing and return routing to vlan2
Cisco1841：configured default routing to another network and return routing to vlan2
Cisco3750：divided vlan1（4 port）and vlan2（1、2、3 port），configured vlan address respectively。The address of 1、2port link with usg3040 and cisco1841 are configured same as vlan2，configured default routing to ADSL exit.
Pc part：different network with server，gateway is vlan1 address
Server part： gateway to usg3040，or cisco1841
Fault：if server gateway to cisco1841，pc can access in server by public network or private network；if server gateway to usg3040，pc can only access in server by public network