Siemens Gigaset C450 IP User Manual
Page 54
53
Web configurator
Gigaset C450 IP / Greek eng / A31008-M1713-T151-2-8U19 / web_server.fm / 19.9.06
Ve
rs
ion 4,
16
.09.
2005
Use random ports
Click on the option
Yes
, if you do not
want the phone to use fixed ports for
SIP port
and
RTP port
, but rather to use
any free ports.
The use of random ports makes sense if
you want several phones to be oper-
ated on the same router with NAT. The
phones must then use different ports
so that the router's NAT is only able to
forward incoming calls and voice data
to one (the intended) phone.
If you click on
No
, the phone will use
the ports specified in
SIP port
and
RTP
port
.
Area:
Network
If your phone is connected to a router with
NAT (Network Address Translation) and/or
Firewall, you must make a few settings in
this area so that your phone can be
reached from the Internet (i.e. can be
addressed).
Through NAT, the IP addresses of subscrib-
ers in the LAN are concealed behind the
public IP address of the router.
For incoming calls
If port forwarding is activated or a DMZ is
set up for the phone on the router, no spe-
cial settings are required for incoming
calls.
If this is not the case, an entry in the NAT
routing table (in the router) is necessary in
order for the phone to be reached. This
entry is created when the phone is regis-
tered with the SIP service. In the interest
of security, this entry is automatically
deleted at certain intervals (session time-
out). The phone must therefore confirm
its registration at certain intervals (see
, page 53), so that the
entry stays in the routing table.
For outgoing calls
The phone needs its public address in
order to receive caller voice data.
There are two possibilities:
u
The phone requests the public address
from a STUN server on the Internet
(Simple Transversal of UDP over NAT).
STUN can only be used with asymmet-
ric NATs and non-blocking firewalls.
u
The phone does not direct the connec-
tion request to the SIP proxy but to an
outbound proxy on the Internet that
supplies the data packets along with
the public address.
The STUN server and outbound proxy are
used alternately to work around the NAT/
firewall in the router.
STUN enabled
Click on
Yes
if you want your phone to
use STUN as soon as it is used on a
router with asymmetric NAT.
STUN server
Enter the (fully-qualified) DNS name or
the IP address of the STUN server on
the Internet.
If you selected the option
Yes
in the
STUN enabled
field, you must enter a
STUN server
here.
STUN port
Enter the number of the communica-
tion port on the STUN server. The
default port is 3478.
NAT refresh time
Specify the intervals at which you want
the phone to update its entry in the
NAT routing table. Specify an interval in
seconds that is a little smaller than the
NAT session timeout.
As a rule you should not change the
preconfigured value for the
NAT refresh
time
.