I have recently learned that one of the most common issues with the VoIP setup of an Avaya IP Office 500 IP PBX is the routing of the IP packets. While the IP Office offers 2 Ethernet interface called LAN1 and LAN2 with configuration fields for the local IP address and netmask, there is no easy possibility to setup a default route to the internet.
In the above example the Avaya IP Office 500 uses LAN2 o connect to the Internet, LAN2 also has a local IP address of 172.16.0.2 and a netmask of 255.255.255.240. In order to allow the IP Office to access the Internet you need to add a static route in the “IP Route” section, right-click onto the section and choose add. For our example we add a default route via the gateway with IP address 172.16.0.1 on interface LAN2.
Be sure to save the configuration and transfer it to the IP Office. Now you are ready to configure the VoIP part of the IP Office. See here for an example.