Symptom

The customer's live network is divided into network areas a, b, and c, as shown in the following figure. Network areas a and b are isolated. Both network area a and network area b can communicate with network area c. U1910 and U1930 users make outgoing calls through the U2990.

If the U1910 and U1930 are connected directly to the U2990 through the SIP trunk, the U1910 users and U1930 users cannot call each other. To ensure that the U1910 users and U1930 users can call each other, connect the U1910 and U1930 to the SBC through the SIP trunk and connect the U2990 to the SBC through the SIP trunk.

However, some users in network area c need to use the intranet Wi-Fi. If NAT exists on the network, the SBC needs to be used as the agency of U2990 port 5060 for Wi-Fi users.

On the live network, the U1930 and Acme SBC are successfully connected through the SIP trunk, and the Acme SBC and U2990 are successfully connected through the SIP trunk. After the connection, phone terminals under the U1930 cannot dial phone terminals registered with the U2990. For example, the phone terminal number 25805301 is registered with the U1930 and the phone terminal number 25805999 is registered with the U2990. If the U1930 is connected directly (not through the SBC) to the U2990 through the SIP trunk, a call is successfully made from 25805301 to 25805999.

The Wireshark is used to capture packets on the Acme SBC when the number 25805301 registered with the U1930 dials the number 25805999 registered with the U2990. The following SIP message is found.

Possible Cause

Digits 2580 are the call prefix configured on the U1930. The SupportInfo parameter on the U1930 indicates whether to support the function of delivering digits one by one. Assume that the U1930 is directly connected to the U2990 through the SIP trunk and the phone terminal number 25805301 registered with the U1930 dials the number 25805999. When the digits 2580 are dialed, the U1930 sends the digits, which are the call prefix configured on the U1930, to the U2990 and the U2990 is waiting for an INFO message from the U1930. Then the U1930 sends digits 5999 one by one to the U2990 and sends the INFO message when all the four digits are sent. When the U2990 receives the INFO message from the U1930, the U2990 queries the entire eight digits locally and select a proper route.

This mechanism, however, is not available on the Acme SBC. When the U1930 sends the call prefix 2580 to the SBC, the SBC sends the call prefix to the U2990. The U2990 fails to find the number 2580 locally. Therefore, the call is not connected.

Solution

1. Log in to the U1930 using a command-line tool.
2. Run the enable command and the config terminal command. The configuration page is displayed.
3. Run the show protocol sip command to query the domain name, such as u1980, of the corresponding office route.
4. Run the config protocol sip officeno 0 domainname u1980 supportinfo no command to disable the supportinfo parameter.

   

5. Run the show protocol sip command and verify that the supportinfo parameter is disabled.

   
   

6. After the parameter is disabled, use the number 25805301 under the U1930 to dial the number 25805999 under the U2990 again. The value of supportinfo is no. Therefore, the U1930 collects all the eight digits and then sends the entire number to the SBC, instead of sending digits one by one. The call is connected.