One way audio issue

[Baasanjargal_Ts]

There's facing an one way audio issue. 

Therea are two LANs. PBX located networks ip phones are normally (two way audio call is successful).

But another subnet, which is not located pbx's ip phones are facing one way audio call issue.

[PhoneBoy]

A network diagram would be really helpful as would the version/JHF level.

[Maarten_Sjouw]

Keep in mind that you need to open the UDP high port range defined in the PBX, in both directions, between the networks your phones are in.
The audio stream is a connection directly between both phones having a call. The audio does not run over the PBX.

[G_W_Albrecht]

See:

R80.30 VoIP Administration Guide

How to secure VoIP

sk14587: Howto configureVoIP(H.323)

sk95369: ATRG: VoIP

sk98755: H323 VoIPnot connecting / one sided media

sk115038: Audio in SIP call is only in one way on SNX client / Remote Access VPN client when Office ...

sk102208: When remote access users connect to the local 600 / 1100 VPN server and establish VoIP Cal...