A1 VoIP RequirementsGetting Started 49Is network address translation (NAT/NAPT) disabled?In a network where address translation techniques (e.g., NAT/NAPT) are used to convert betweenglobal and local IP addresses, VoIP communications based on the H.323 protocol cannot be carriedout appropriately. Generally, NAT/NAPT are features that are available with routers.NoteIf the router on the network supports the "H.323 NAT" feature, it may be possible to have VoIPcommunications over the network. For more information, consult your network administrator.Does only a single router provide access to the IP network?In a dual network, 2 routers provide access to the IP network as shown in the diagram below.However, the VoIP Gateway Card cannot take the advantage of having 2 routers as access points tothe IP network.For example, if router A, whose IP address is assigned as the default gateway IP address of the card,fails, VoIP communications are no longer possible; the card is not able to switch its default gatewayfrom router A to router B to access the IP network. For more details about the default gateway setting,refer to "2.2.1 Network Parameters" of the VoIP Gateway Card Programming Guide.Router(NAT/NAPT enabled)IP NetworkGlobal IP Address DomainLocal IP Address DomainIP NetworkRouter A Router BDefault gatewayof the card:Router A
