Caller cannot hear user, user can hear caller

[fitzgerald.d]

Good morning,

I'm experiencing a problem with our CUCM (ver 6.1.2). We receive or make a call and when answered the caller cannot hear us, but we can hear them. This is only happening with the occasional phone call, and doesn’t seem to be a problem regarding where the call has originated. it doesn't matter if it's come long distance, or locally. However the problem has not been reported happening on any internal calls. I’ve restarted the call manager, and there have been no changes to the system I am aware of.

Anyone have an idea about what may be causing this? Could it be an issue with the TELCO?

Thank you

[acampbell]

Duncan,

One way transmission in VOIP is usually an IP routing issue.

Make sure that the PSTN gateway has IP connectivity to all the phones

Also if your gateway has multiple IP interface then you need to bind ONE of these to

H323, MGCP or SIP

E.G

H323 ##
!
!
!
interface Loopback0
description VOIP-GW_01 LOOPBACK 0 ALWAYS UP
ip address 10.182.255.254 255.255.255.255
h323-gateway voip bind srcaddr 10.182.255.254
!

SIP ##
!
!
!
voice service voip
sip
bind control source-interface LOOPBACK 0
bind media source-interface LOOPBACK 0
!

MGCP  ##
!
!
!
mgcp
!
mgcp bind control source-interface LOOPBACK 0
mgcp bind media source-interface LOOPBACK 0
!
mgcp ip qos dscp ef media
mgcp ip qos dscp cs3 sig
!

HTH

Alex