Issue description
A customer encountered an issue to make calls between two sites using a U1960 unified gateway. The customer has two sites, one in Paris and another in Bordeaux. U1960 unified gateway is in Paris and some IP phones are in Bordeaux registered to the U1960 from Paris site by IPsec VPN.
All the telephone models are eSpace 7950 and they can call each other. The telephones in Paris can make calls outside, but the ones in Bordeaux can't (one way audio issue). The Paris site subnet is 192.168.1.1/24 and the Bordeaux subnet is 192.168.2.1/24.
Handling process
In order to further troubleshoot the reported issue we have requested the following pieces of information:
Network topology
The IP address assignation for Bordeaux - IP ranges from 192.168.2.1-254. For the Paris Office, the IP ranges from 192.168.1.1 - 192.168.1.254.
How does the oitgoing call fail exactly? When the customer called their phone, the phone could ring; however, when they picked up, they couldn't hear any voice.
The type of trunk used to connect to the PSTN (SIP, PRA, AT0, etc.) - SIP Trunk
Can 7950 phones registered directly to Paris call the 7950 phones from the Bordeaux site (registered in Paris via IPSec VPN)? - Yes, 7950 phones can call each other, either from Paris or Bordeaux working well.
1. Network trace (signaling trace) performed via LMT while the issue was being reproduced.
The firmware version of eSpace U1960 as per below:
2. Network capture extracted using port mirroring function of the eSpace 7950
3. Tried to use 192.168.2.48 (Bordeaux phone) to ping 130.93.X.X to see if it passes and then capture on Bordeaux phone to see if it passed
After the customer provided the results, the ping test was in order so we did not know if the Bordeaux site (192.168.2.0/24) will go to 217.15.X.X through firewall. There is no logical link diagram between the two IP's, so we requested to mirror the U1900 network port on the switch and feedback the result.
As it can be seen below, the RTP traffic is only one way:
We needed to check if there was any RTP packet sent from the operator 217.15.X.X to the firewall. After the IPSec VPN passes through this IPSec VPN, the ARs go out to connect to the carrier.
The IP phones on the 192.168.1.0/24 and 192.168.2.0/24 segments are registered to U1960 (IP address: 192.168.1.2). The IP phone of 192.168.1.0/24 is registered to U1960 through IPSec VPN. When the IP phone of 192.168.1.0/24 makes an external call, it is going to go out of the AR.
Root cause
The carrier's public IP address had not been configured at VPN in order to make sure the media packages could go through the network to each phone.
Solution
Configure the carrier public IP address at the VPN side to make sure that the media traffic can go through the network to each phone.
