VoIP gateway IP400 version 5.01
Page 143
Table 22
Troubleshooting
NAT and firewalls
If there is a firewall protecting your network from the Internet and you want to
establish connections between your gateway and remote terminals via the Inter-
net, you need to ensure that the firewall is configured appropriately.
Firewalls usually have two jobs. They control access to equipment and areas
within your network and they implement IP address translation in networks that
do not have their own regular network address (so called “NAT”, network address
translation). “NAT” can also be implemented by routers.
Symptom
Description
Action
The gateway is con-
nected to the network
behind a “firewall” and
no connections can be
established to other
VoIP devices.
The firewall does
not support the
H.323 protocol.
• Activate “H.323 Firewall-
ing” in your firewall soft-
ware and if necessary
“H.323 NAT” too. Refer to
your firewall documenta-
tion for this purpose.
• Refer to the Section “NAT
and firewalls” from
page 143.
You are using the
gwload.exe
utility.
Uploading of new
firmware fails, although
the gateway is found.
Your computer's
arp-cache con-
tains incorrect
information.
• Clear the computer's arp-
cache. To do this with a
Windows PC, use the com-
mand
arp –d
ip-addr
.
Fax transmissions are
interrupted.
T.38 is not
authorised in the
gateway defini-
tion.
• Activate the T.38 protocol
(see from page 73
onwards).
Fax transmissions are
interrupted, in particu-
lar with lengthy faxes.
The gateway and
PBX to which the
fax machine are
not connected to
a synchronous
ISDN clock.
•
Provide correct clock syn-
chronisation (see page
53).