asterisk02*CLI> iax2 show peers
Name/Username Host Mask Port Status
...
asterisk01 192.168.206.4 (S) 255.255.255.255 4569 UNREACHABLE
...
root@asterisk02:~# ping 192.168.206.4
PING 192.168.206.4 (192.168.206.4) 56(84) bytes of data.
64 bytes from 192.168.206.4: icmp_req=1 ttl=62 time=20.9 ms
64 bytes from 192.168.206.4: icmp_req=2 ttl=62 time=14.3 ms
^C
Помогает
/etc/init.d/asterisk restart