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Level 1
Level 1

We seem to be having RTP issues with an Adtran600 (see below) and it all seems to point to my Cat6500- Count for RTP VOICE RX is 0. Any ideas?

Gateway Stats │ Gateway Link Status Up

POTS Stats │ Endpoints Active 0

Endpoint Stats│ Rx Declined Pkts 0

│ Dropped Rx Bad Pkts 0

│ MGCP Tx Packet Count 180

│ MGCP Rx Packet Count 180

│ RTP Voice Tx Packet Count 24257

│ RTP Voice Rx Packet Count 0

│ RTP Rx Seq Num Errors 0

│ ABCD Tx Packet Count 0

│ ABCD Rx Packet Count 0

4 Replies 4

paolo bevilacqua
Hall of Fame
Hall of Fame

Sorry, you did not presented not even an half of the details needed to understand your problem.

What are the devices involved ?

How they are connected ?

How they are configured ?

What is the goal ?

I have an Adtran 600IAD

Plugged directly into a Cat6500

that traffic flows over Cisco15454 (fiber tranport to other office)

At the other office the 15454 plugs into a

Allied Switch and also to a Metaswitch (VOIP soft switch.

When doing a trace the Cat6500 looks like it isn't getting any RTP count. I am not sure if this is an access list issue or not.

The goal it to have MGCP and RTP traffic right now the voice traffic is one way. Can call off the 600 to someone but can't hear what they are saying.


I believe that voice card on the cat 6K are not supported by Cisco for use with anything else but cisco call manager. I'm afraid you will have to start looking at traces and get support from Metaswitch as well.

From a TAC engineer's perspective, a problem that is 100% defined is 50% resolved ...

So here is what we now know :

You have a 3rd party voip device plugged into a Cat6K switch. The switch has an optical connection to a remote site that has a another switch that connects to a MGCP Call Agent.

I don't believe there is any particular Cisco voice blade installed in the Cat6K, so we are not talking about a Cisco specific voice issue here.

Based on the stats from the Adtran device, you are seeing TX and RX MGCP control traffic so you have an open session to the call agent. This means you have IP connectivity on UDP port 2427.

Since the RTP RX counter is zero, then it is apparent no media is getting to the IAD.

And here is what we don't know :

Is the entire network layer 2 switched network (no routing) or is there layer 3 routing ?

Is there any packet filtering being done on the CatK ?

Are the RTP media flows actually getting to Cat6K in the first place ?

How many connections does the Cat6K have the rest of the network?

Before jumping to conclusions about possible reasons such as access lists, you need to follow the RTP media path from the source in a logical approach to determine where it is failing.

Assuming the Optical connection is the only ingress point into the Cat6K, do a SPAN session on this port to another port that has a PC running wireshark, and make a test call.

Need help doing the SPAN -

Get a packet capture and confirm if you have RTP packets coming into the switch in the first place. If you do see RTP, then you can concentrate on your Cat6K switch.

If you don't see any RTP, then do the SPAN or similar off the Allied switch and see if it is getting this far.

Follow the RTP back to the source and you will find your answer.