Phones not registering all of a sudden

Hi, I run version 2.6.06. All of a sudden, our phones are dead. I did a sip show peers and I get host unspecified for all my extensions. I see a from pstn host and I don’t recognize the ip address. Below is the sip show peers result:

Name/username Host Dyn Nat ACL Port Status
from-pstn 64.154.41.100 N 5060 Unmonitored
311 (Unspecified) D N A 0 UNKNOWN
310 (Unspecified) D N A 0 UNKNOWN
309 (Unspecified) D N A 0 UNKNOWN
306 (Unspecified) D N A 0 UNKNOWN
305 (Unspecified) D N A 0 UNKNOWN
304 (Unspecified) D N A 0 UNKNOWN
303 (Unspecified) D N A 0 UNKNOWN
302 (Unspecified) D N A 0 UNKNOWN
301 (Unspecified) D N A 0 UNKNOWN

any help would be appreciated.