IP Phone Ringing but no voice

[Jackong]

Hello

I am experiencing some strange issue with my VOIP in 1 of my branches.  our branches are connected thru IP VPN and 1 of our branches are able to call our office in HQ (ringing but no voice) other branches are able to call our office without any issue.  i tried traceroute from the branches with issue couple of times as per result below.

1st tracert (problem branch)

Problem_RTR# traceroute 10.1.5.57 source 10.10.1.1 port 180
Type escape sequence to abort.
Tracing the route to 10.1.5.57
VRF info: (vrf in name/id, vrf out name/id)
1 172.18.112.117 12 msec 15 msec 25 msec
2 172.18.138.210 [AS 65000] 31 msec 29 msec 29 msec
3 192.168.100.1 30 msec 38 msec 27 msec
4 10.1.5.57 [AS 29684] 27 msec * 28 msec

2nd time trace route

Problem_RTR# traceroute 10.1.5.57 source 10.10.1.1 port 200
Type escape sequence to abort.
Tracing the route to 10.1.5.57
VRF info: (vrf in name/id, vrf out name/id)
1 172.18.112.117 12 msec 12 msec 11 msec
2 172.18.138.210 [AS 65000] 30 msec 28 msec 28 msec
3 192.168.100.1 27 msec 27 msec 28 msec
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *

other branches without issue trace route

1st trace route

No_Problem_RTR#traceroute 10.1.5.57 source 10.12.1.1 port 200

Type escape sequence to abort.
Tracing the route to 10.1.5.57

1 172.16.199.125 32 msec 28 msec 28 msec
2 172.18.138.210 [AS 65000] 28 msec 32 msec 36 msec
3 192.168.100.1 [AS 65000] 32 msec 36 msec 28 msec
4 10.1.5.57 [AS 29684] 32 msec * 32 msec

[Flavio Miranda]

@Jackong 

 Your test does not allow any conclusion as you did it differently. Not sure why you are using port on the trace route but if you are going to use, test with the same port so that the test make sense

 In situation where we have signaling but not voice, usually means NAT problem or firewall. The RTP traffic, which is point  to point is not getting from the caller to the calling.

[Nithin Eluvathingal]

It’s a routing problem. The signaling will be handled by CUCM, and you might have a router to and from the phone subnet in the branch to the CUCM in the HQ. However, when the call is answered, the media flows from phone to phone. You might have a route  missing from the branch phones to the HQ phone subnet and the other branch phone subnet, and vice versa.

When tracing the router, keep the source IP  as the phone subnet; there’s no need to use the port. If you need to trace with the port, use the port used for the RTP streams, as you don’t hear the voice, which is an RTP stream.

Additionally, you need to identify which side is unable to hear the voice and trace from that side.

For example, if A calls B and A can hear B but B cannot hear A, it means packets from A are not reaching B’s phone, likely due to network reachability issues from A to B.

Signaling is taken care of by CUCM, and media will be direct phone-to-phone unless MTP is invoked.

[Jackong]

Hi!

i have checked my firewall which was i think blocking and i check and issue command " sh shun " in FWSM and displays blocking (10.10.1.1 - router sub interface for ip phone) and (10.10.1.23 - ip phone).  i did negate the shun command to release those IP and now it is working fine... additional to my query why or any reason suddenly my FWSM is blocking that network traffic which was working for long time....

[Roger Kallberg]

No one but someone who has access to your specific system landscape can answer that question for you.