Different subnets

My configuration has two subnets 10.0.1.x and 10.0.2.x/24. I have the asterisk server running, and I have two phones A on and B on I have setup phones A and B with static IP addresses and set their SIP server each to Both A and B register okay. When B tries to call A it says “UNAUTHORIZED” and the call doesn’t connect. Is there something that is needed to enable a phone that is on a different subnet than the asterisk server to make and receive calls?

No. Asterisk has no concept of sub-nets, with exception of localnets, and access control. The phones will not even have those. Both will rely on lower layers to handle the subnets. Failure to route properly should not produce an authentication error.