Call Signaling issues with IP Phone behind Cisco ASA on DSL over tunnel

Unanswered Question
Jul 28th, 2009


I have recently set up a Lan-to-Lan ipsec tunnel between our corporate Cisco ASA 5520 firewall and a remote office with a Cisco ASA 5505 over DSL. Tunnel is up fine, all data is working normally. My problem lies in the Avaya 4620 ip phones I have behind the ASA 5505 at the remote office. Voice quality over the connection is great but we have continual issues with the phones I believe to be a voice signaling issues. Some of the symptoms include:

1.) Slow response on the phone to get a dial tone.

2.) delays from the phone to register that the receiver has been hung up.

3.) Calls dropping completely in the middle of a call.

4.) Calls ringing through to the phone, but when picked up, no dial tone, and they cannot get the call.

This one has me puzzled. We do have approx 20 telecommuters who use the avaya vpn remote phone which terminates to the corporate firewall and those phones have no issues what-so-ever. I have my ipsec tunnel configured between the coporate office and the remote office with the same ike and ipsec parameters as the avaya vpn remote phones yet for whatever reason the phones behind that asa at the remote office are really not functioning as I projected they would. Has anyone run into this and can give me a few ideas. Thank you all in advance for your assistance, as always, its greatly appreciated. Cheers!

I have this problem too.
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bgrunewald Wed, 07/29/2009 - 18:17

Sounds like the signaling protocol for the phones is not being give proper QoS. Since it is not SCCP, you may have to do some extra config to make the magic happen.

Can you associate the problems to high data loads?

stogyman_ Thu, 07/30/2009 - 07:41

Thank you for your response to my issue. Here is what I have done for Qos on the small ASA in at the remote office:

class-map voip-sig

match dscp af31

class-map voip-rtp

match dscp ef

policy-map voip-qos-policy

class voip-sig


class voip-rtp


service-policy voip-qos-policy interface outside

priority-queue outside

tx-ring-lmit 3

queue-limit 220

MISMTFC01# sh service-policy int out

Interface outside:

Service-policy: voip-qos-policy

Class-map: voip-sig


Interface outside: aggregate drop 0, aggregate transmit 915354

Class-map: voip-rtp


Interface outside: aggregate drop 0, aggregate transmit 915354

I have a similar configuration on the corporate ASA. I get the same output when I run that same command from my ASA at the corporate office.

A change I performed yesterday on both ASA's was to disable inpsection for H.323 protocol. Since I made that change, the phones have been stable, but I wont be totally convinced until I can monitor this for a few days and put a heavy data load on that line. I will follow up if this solution holds up. Once again, thanks for your response.


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