I’ve recently set up a new FreePBX server with the IP address 10.100.11.18, replacing our old Elastix system. While all SIP phones that were previously using IPs in the 10.100.11.xxx range are working fine.
The problem is that certain SIP phones only work if I change their IP addresses to the 10.100.10.xxx range. I’ve ensured that the local network settings in both SIP settings and Chan_pjsip are configured as 10.100.10.0/23.
Has anyone faced a similar issue, or does anyone have suggestions on how to resolve this? Any help would be greatly appreciated.
Are all SIP phones running the same firmware version? Are they all the same model? Are they configed from a webserver on the phone or from config files from a tftp server? Is there any commonality in the models that only work from the 10.100.10.x IP addressing?
One thing I have run into when changing subnet masks on an established network (going from 255.255.255.0 to 255.255.254.0 for example) is invariably you forget to change a subnet mask somewhere. Another problem is that not all software developers who write firmware completely understand the idea behind subnetting. I’ve run into firmware that only works properly if you use 255.0.0.0 or 255.255.0.0 or 255.255.255.0 as a subnet mask. That’s why I reserve the subnet games of slicing and dicing IPv4 subnets for actual public numbers on the real Internet when working with the real Internet (I was a system admin of an ISP for 10 years a decade ago) and I avoid classless masks with private IP addressing.
The entire point of private IP addressing is to give you unlimited numbers to use in your organization so if you are too big to fit in a Class C then use a Class B subnet and quit being fancy. We know you are smart enough to understand subnetting since you understand what CIDR is you don’t need to prove it to the devices which don’t give a rip if they are on 172.16.x or 10.x.x.x or 192.168.x. The problem is the gear you are working with may have been built by people not as smart as you and their ignorance of what an IPv4 subnet is will gun you.
