Draytek Vigor2820 Series User Manual page 195

Disable Port
RTP
account for each phone port.
DTMF Relay – Display DTMF mode that configured in the
advanced settings page of Phone Index.
The router can support up to 4 VoIP calls simultaneously. In
general, only 3 VoIP calls can be dialed through ISDN at the
same time. If you want to use four ISDN channels, you have to
check this box. When the Phone port is disabled, it could not
be used anymore.
Symmetric RTP – Check this box to invoke the function. To
make the data transmission going through on both ends of
local router and remote router not misleading due to IP lost
(for example, sending data from the public IP of remote router
to the private IP of local router), you can check this box to
solve this problem.
Dynamic RTP Port Start - Specifies the start port for RTP
stream. The default value is 10050.
Dynamic RTP Port End - Specifies the end port for RTP
stream. The default value is 15000.
RTP TOS – It decides the level of VoIP package. Use the
drop down list to choose any one of them.
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Vigor2820 Series User's Guide