3.2. Case II: Two-Site IP PBX
This case describes the typical settings of a two-site network for company B
headquarters B-HQ and its branch B-BR in another country. Assuming each site has
a DSL connection for Internet access. B-HQ has 4 PSTN subscriber lines and B-BR
has 2 lines as shown in Figure 5-2. The provisioning tasks include:
Both sites have staff phones in cubes and offices and utility phones in public
areas.
Each phone has one extension. A utility phones can call extensions within the
site it is in only, while the staff phones can call any extension in both sites without
limitation. B-HQ has extensions 1XX and B-BR has extensions 2XX.
Calls between B-HQ and B-BR use private SIP trunks across Internet. IP PBX at
B-HQ has a static IP address 64.1.0.1 and IP PBX at B-BR has a static IP
address 222.44.0.1.
Only staff phones can call out to PSTN with a prefix 9.
B-HQ staff phones call out starting with 90118621 will relay to B-BR through the
SIP trunk and then hop off to PSTN in B-BR. Similarly, B-BR staff phones call out
starting with 9001408 will relay to B-HQ for PSTN hop-off.
Incoming PSTN calls are answered by auto attendant and could be transferred to
any extension.
