Half-duplex calls from remote users

Unanswered Question
Mar 27th, 2009

I have a call manager 4.1(2) system connected with a 2811 gateway and T1 with remote users who have VPN connections through internet via ASA (attached with 6MB pipe). The T1 is for PSTN calls. Users who call from remote sites (single users with DSL or cablemodem links) to each other (not to central site) will almost always have to make 2 calls. The first call will have one party not able to speak and/or hear the other end. Any ideas??

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Paolo Bevilacqua Fri, 03/27/2009 - 11:59

Most likely these are the firewall/asa/vpn that you have in the audio path,you need to make sure no internal activity is blocked or inspected.

Paolo Bevilacqua Fri, 03/27/2009 - 12:09

Sometime the security appliances behave a little strangely, due to timeouts, etc a flow may or may be not blocked.

Andy Infante Fri, 03/27/2009 - 12:18

Ok, so I do have inspect in global policy...what do I disable?

policy-map global_policy

class inspection_default

inspect dns migrated_dns_map_1

inspect ftp

inspect h323 h225

inspect h323 ras

inspect netbios

inspect rsh

inspect rtsp

inspect sip

inspect sqlnet

inspect sunrpc

inspect tftp

inspect xdmcp

class class-default

Andy Infante Fri, 03/27/2009 - 12:27

Disable all inspection? This is our company firewall. Won't that allow some things to be missed?

Andy Infante Mon, 03/30/2009 - 13:31

Ok, so I've disabled all inspection and the problems are still present. Since not all my users have the same problem, but are fairly consistent with highest bandwidth DSL or cablemodem isp connection, what other options can I tweak to see what makes a difference? Some users have older vpn clients and ip communicator, also some using Anyconnect. Other users have ipsec tunnel with dedicated 803 router and 7912 phone. No consistency in the problems...mostly problems with users on vpn client and softphone.

Andy Infante Tue, 03/31/2009 - 13:05

Should the call appear in the output the whole time is it connected? One user who I tested this with couldn't hear or talk, and even her dialtone came out as clicks and dashes. Voice, if it ever came through was choppy and intermittent. Running command above had the call appear briefly, then no longer, like it was disconnected, but her call to me was still running on both our phones, with no communication possible...how is that?

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