The configuration output below represents the minimum necessary to utilize the Total Access 900 as a SIP device. This serves as a base on which to build a complete SIP configuration. Certain features - such as NAT, DHCP, VPN, QOS, or specific SIP features - are not represented here. Please note that parameters such as WAN and LAN IP addresses, server IP addresses, and voice user extension numbers will need to be changed according to the application. Remember to save by issuing the “copy run start” or “wr” command.
While this template covers an app in which the WAN connection and therefore the SIP server exists out the T1 interface, it should be noted that there are only a few changes needed for an Ethernet-fed config (i.e. behind a DSL/cable modem). Since the SIP trunk is virtual and not cross-connected to any specific physical interface, the unit relies on its gateway of last resort (default route of 0.0.0.0) to decide the interface used to transmit SIP messages. In other words, the IP of your SIP server is a layer 3 destination address treated no differently than any other packet, following the route table to decide its path. Along the same lines, the command “media-gateway ip primary” designates a given interface (Ethernet, PPP, etc) as one that will expect to transmit and receive RTP packets. It merely states “the primary IP of this interface will be a media gateway.” It does not mean “this interface is my primary media gateway” and therefore can be on more than one interface. Generally, the command needs to be on any IP interface expected to send and receive a packetized talk path via RTP. For an Eth-fed app, you will need this command on the Ethernet interface. For a T1-fed app, you will need this command on the layer 2 interface (PPP, HDLC, etc). For apps where both T1 and Eth ports will source/receive RTP (i.e. T1-fed with SIP phones on the LAN), the command will be on both.