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New Member

Dead Air

There is a similiar post to this, but has anyone seen this on a 6608 blade.

Incoming or outgoing calls will dial, ring, and connect, but both parties hear nothing.

7 REPLIES
Cisco Employee

Re: Dead Air

From my experience this is usually a routing issue. Call setup takes place from the 6608 to the CallManager, and then from the CallManager to the IP phone. The audio stream, however, is direct from the 6608 to the IP phone. Can you ping from the 6k to the IP address of the IP phone (don't worry that not all pings are returned, the IP phones only returns a portion to prevent DOS attacks from affecting it)?

New Member

Re: Dead Air

Yes, I can ping from the 6K to the IP phone. The sc0 int is in a different subnet than the phone, but both subnets are on an MSFC in a core 6509 which is routing all VLANS.

Cisco Employee

Re: Dead Air

hmmmm, did you do a ping or an extended ping from the MSFC? If possible, do an extended ping with the source address being the IP of the 6608 port. Info on extended ping can be found at http://www.cisco.com/warp/public/105/ext_ping_trace.html

That will verify that packets can get back & forth between the 6608 port and the ip phone.

New Member

Re: Dead Air

Actually, you want to test a ping from the phone to the voice port on the 6608 blade. Each port has its own MAC and IP address. To test connectivity, put a PC on the phone VLAN and ping the T1 port on the switch. To get the address of the T1 voice port on the Cat6K, use the "show port voice" command.

On another note, are you using DHCP to assign addresses to the T1 ports or are they static? I had some issues early on using DHCP to address the 6608 ports, so I've been hardcoding the addresses ever since. Also, if you have T1 ports that are not used for voice, conferencing, or transcoding, I'd recommend that you disable them.

New Member

Re: Dead Air

We had this problem. It turned out to be a bad DSP on the 6608 blade. The call would set up, but no audio stream would be sent. We worked with TAC and discovered the problem after we move the T1/PRI definition to another port on the module and the problem went away.

New Member

Re: Dead Air

Dan,

Have you tried all the above and still have the problem or is the problem resolved now? Your feedback will be very much appreciated.

As part of your resolution process perhaps you'll consider like to plugging in a sniffer / network monitoring tool for further analysis.

A codec mismatch could however result in this predictment.

Thanks - George.

New Member

Re: Dead Air

Pings to and from the 6608 have been fine. I had the PSTN carrier rebuild all the routes coming into the two PRIs on the 6608 and that seems to have fixed it.

Thanks everyone for the help.

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