one way audio on IP to PSTN

Unanswered Question
Aug 15th, 2007
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New setup, everything seems to checkout fine, except for this:

Caller from PSTN to IP phone.

Audio both ways

IP on PSTN with remote caller

Audio one way. (remote side cant hear me)

One the LAN side, IP to IP phone works fine, No audio problems.'

So I know my problem is between the voice gateway and IP phone.

Phones are on VLAN 100

Data is on VLAN 200

Switchports are configured to Auto everywhere. (between phones, VG and Switch)

On the phone, I dont see any jitters, drop ped packets, etc. (hitting ??)

IP Phone:

gw (VLAN 100 on switch)


Default route


no default route sets



I ping:

from VG to IP phone ( to

From switch to IP phone ( to

From VG to VLAN100 ( to

The only thing odd I see is that when I do an extended ping to the IP phone from the switch OR the VG, i get 16 percent loss in data. Basically 84/100 sucessful pings.

Any hints?


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paolo bevilacqua Wed, 08/15/2007 - 17:01
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Worry not, the phones by design doesn't reply all the pings.

What is the VG and what SW do you have on it. Also what FW on the phone and if you are using CCM which version and which protocol to the VG.

Tommer Catlin Thu, 08/16/2007 - 09:04
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12.2(25)SEE3 switch 3460

VG 12.4

CCM 5.1

Protcol NI2 (global) at VG

phone load 41.8-2-2sr2s


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