If a SIP trunk needs to be authenticated against multiple IP addresses, do as follows:
- Login to the administration interface
- Navigate to 'Trunks'
- Add/Edit SIP trunk
- Set 'Type'='peer'
- Set 'Insecure'='very'
- Set 'Host'='1.2.3.0/255.255.255.0' (range in format 'start/end' ip address)
- Click on 'Save'