My company has 2 sites each configured with cisco asa5510 with vpn. Originally site A firewall is configured with only ipsec passthrough while site B is configured with both ipsec passthrough and nat traversal. Users at site B could vpn into site A but unable to access any resources at A. However from my home, i could vpn into site A and access network resources within site A. I then added nat-traversal to site A firewall to resolve the problem. Why is this so? Can someone also explain the difference between nat traversal and ipsec passthru? Thks in advance.