Siemens Gigaset C450 IP User Manual

Page 54

Web configurator

Gigaset C450 IP / Greek eng / A31008-M1713-T151-2-8U19 / web_server.fm / 19.9.06

ion 4,

.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

, 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

NAT refresh time

, 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:

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.

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