[asterisk-users] Why asterisk down when inet server down?

[sean darcy]

We have a 10.10.0.0 internal network. The asterisk server - 10.10.10.180 
- has a PRI connection to a T-1. Another server is the router to the 
internet. All phones in the office and the workstations are on the network.

Most of the internal phones are aastra 9133i's. Here the network config 
from a phone:

Network Settings

    Basic Network Settings
    DHCP                         [ ] Enabled
    IP Address                   10.10.10.44_________
    Subnet Mask                  255.255.255.0_______
    Gateway                      10.10.10.180________
    Primary DNS                  10.10.10.180________
    Secondary DNS                0.0.0.0_____________

If the network server is down, the phones go out of service. From a 
workstation I can still ssh into the asterisk server. But for some 
reason the phones don't work. I can console dial out from the server. 
The asterisk server doesn't need the internet for connectivity.

Why do the internal phones go down?

sean