Specifications

Chapter 6 Configuring VoIP
Additional VoIP Dial-Peer Configurations
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Catalyst 4224 Access Gateway Switch Software Configuration Guide
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The default for the codec command is g729r8, which is normally the most
desirable setting. However, if you are operating on a high-bandwidth network and
voice quality is of the highest importance, you should configure the codec
command for g711alaw or ulaw. Using g711alaw results in better voice quality,
but it also requires higher bandwidth usage for voice.
For example, to specify a codec rate of g711alaw for VoIP dial peer 108, enter
the following:
c4224(config)# dial-peer voice 108 voip
c4224(config-dial-peer)# codec g711alaw
Note Prior to Cisco IOS Release 12.0(5)T, g729r8 is implemented in the pre-IETF
format; thereafter, it is implemented in the standard IETF format. When new
images, such as Release 12.0(5)T or later, interoperate with older versions of
VoIP (when the g729r8 codec was not compliant with the IETF standard), users
can hear garbled voices and ringback on either side of the connection. To avoid
this problem, configure the dial peers with the g729r8 pre-ietf argument.
Configure VAD for a VoIP Dial Peer
To disable the transmission of silence packets and enable VAD for a selected
VoIP dial peer, use the following global configuration commands:
The vad command is enabled by default, which is normally the most desirable
setting. If you are operating on a high-bandwidth network and voice quality is of
the highest importance, you should disable VAD. Disabling VAD results in better
voice quality, but it also requires higher bandwidth usage for voice.
Table 6-10 Commands to Disable the Transmission of Silence Packets
Task Command
Step 1
Enter dial peer configuration mode to configure a VoIP
dial peer.
dial-peer voice number voip
Step 2
Disable the transmission of silence packets.
vad