Important Settings; Nat Settings; Dtmf Methods; Preferred Vocoder (Codec) - Grandstream Networks GXW400X User Manual

http://www.grandstream.com/products/gxw_series/gxw40xx/documents/gxw40xx_gui.zip .
the following link:

IMPORTANT SETTINGS

The end-user must configure the following settings according to the local environment.
NOTE: Most settings on the web configuration pages are set to the default values.

NAT SETTINGS

If you plan to keep the gateway within a private network behind a firewall, we recommend using STUN
Server. The following three (3) settings are useful in the STUN Server scenario:
1. STUN Server (under Advanced Settings webpage)
Enter a STUN Server IP (or FQDN) that you may have, or look up a free public STUN Server on the
internet and enter it on this field. If using Public IP, keep this field blank.
2. Use Random Ports (under Advanced Settings webpage)
It really depends on your network settings, so set this parameter to Yes or No, whichever works.
Generally if you have multiple IP devices under the same network, it should be set to Yes. If using a
Public IP address, set this parameter to No.
3. NAT Traversal (under the Profile web pages)
Set this to Yes when gateway is behind firewall on a private network.

DTMF METHODS

DTMF Settings are in Profile pages.

DTMF in-audio

DTMF via RTP (RFC2833)

DTMF via SIP INFO
You can enable set priority of DTMF methods according to your preference, from Priority 1 to 3. This
setting should be based on your server DTMF setting.

PREFERRED VOCODER (CODEC)

The GXW40XX supports a broad range of voice codecs. Under Profile web pages, choose your preferred
order of different codecs:

PCMU/A (or G711µ/a)

G729 A/B/E
FIRMWARE VERSION 1.0.10.9
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