This is on my static ip address side, we'll call this the "server"

[B002_B020]
host=dynamic
type=friend
username=B002_B020
password=passwordpassword
context=from-internal
qualify=yes

on the "client" side

[B002_B020]
host=voip.dc.mydomain.com
type=friend
username=B002_B020
password=passwordpassword
context=from-internal
qualify=yes

register => B002_B020:passwordpassword@voip.dc.mydomain.com

#############################
SERVER: iax2 show peers
Ares*CLI> iax2 show peers
Name/Username    Host                 Mask             Port          Status
B002_B020/B002_  (Unspecified)   (D)  255.255.255.255  0             UNKNOWN


#############################
client: iax2 show peers
SoCal*CLI> iax2 show peers
Name/Username    Host                 Mask             Port          Status
B002_B020/B002_  216.218.XX.XX  (S)  255.255.255.255  4569          OK (19 ms)
(The ip address above is blacked out, but is resolved correctly)

(Port 4569 UDP on the server is set to allow all traffic in, no restrictions on outbound traffic)

and on the client, i keep seeing this msg:

[Jan 14 20:57:32] NOTICE[1110]: chan_iax2.c:8558 socket_process: Registration of 'B002_B020' rejected: '<unknown>' from: '216.218.XX.XX'

No other messages that indicate any issues.. 'iax2 set debug'  doesnt seem to help much either