Description for problem
During the voice call, either one party, or neither party can hear the audio.
Analysis
1. Check whether the two networks can communicate with each other.
2. There is a NAT mapping in the networking.
3. The voice codec between devices is different.
Case
A company uses U1980 as a voice gateway to connect SIP trunks. A single-pass fault occurs in the voice of the IP phone user on the branch U1930.
Networking: U1980----(SIP)----U1930
Analysis
1. Check if the network between U1980 and U1930 is normal.
2. Check whether the network between the two terminals is interconnected. After checking the network between the terminals on both sides, check that the network on one side is not added to the other side; modify the network route, or modify the U1980 and U1930 to directly relay to the PRA.
Summary
For single-pass or double-no-pass problems, the general analysis process is as follows:
1. Check whether the network on both sides is normal and pass the ping command.
2. Check whether there is a NAT mapping in the networking.
3. Grab the network packet analysis to see if there is the same codec on both sides;
4. Grab the network packet to analyze the RTP flow.
