User guide

SIP Telephony 119
Voice over IP (VoIP)
connection. To avoid this problem, the IP address of a
workstation computer or telephone visible on the Internet is
determined using a STUN server (STUN: Simple Traversal of
UDP over NAT). You can ask your SIP provider for the STUN
server’s IP address and port number. If you don’t need a STUN
server, leave the SIP Provider field empty.
z For direct SIP telephony using Forum 523/524, only SIP IDs
consisting of numbers for identifying subscribers registered
with the SIP provider specified can be addressed
z You can integrate an external SIP connection in the
Telephony: Trunks: Route menu into the route
configuration. You can use a network provider rule to specify
the routing of numbers within a specific range to use SIP
telephony as a preference (see also PBX Networking, under
Configuration starting on page 161).
You can configure SIP connections in the Configurator on the
pages Telephony: Trunks: SIP provider and Telephony:
Trunks: SIP trunks. Enter the technical attributes of a specific
SIP provider, such as the IP addresses for the registrar and the
STUN server under SIP provider. Under SIP trunks enter the
information for an existing SIP account, such as the user name,
password, assigned call number and the maximum number of
simultaneous calls possible.
For extension-capable SIP-DDI lines, you can, as needed, make
additional settings on the Telephony: Trunks: SIP Provider
page. Assigning extension call numbers and internal subscribers is
configured on the pages under Telephony: Call Distribution
(Incoming DDI or Outgoing DDI). Please note the explanations
on these pages in the online help. Furthermore, assigning exten-
sions using placeholders (“wildcards”) is possible. The online help
offers an explanation under the keyword Call Number Mapping.
Internal SIP Subscribers
The Forum 523/524 becomes available as the SIP server for inter-
nal SIP subscriber telephony switching services. SIP telephones
connected via LAN or SIP programmes installed on workstation
computers can thus establish connections to all other devices or