Registering SIP phones

I am currently running CentOS 4 with Asterisk installed with no gui interface installed.

I am experiencing an issue with registering a SIP Phone.

I have been able to register 4 out of 5 SIP phones. But Asterisk is refusing to register the last phone. SIP phone 223 is not registering, phone displays a registering state for two days now. Any suggestions why it is not working?

(The sip.config file is scripted to run more then 5 phones at testing phase at the moment)

Below is the current SIP.cfg file content: -

[general]
context=default ; Default context for incoming calls
; defaults to “asterisk”
; Realms MUST be globally unique according to RFC 3261
; Set this to your host name or domain name
bindport=5060 ; UDP Port to bind to (SIP standard port is 5060)
bindaddr=172.16.0.6 ; IP address to bind to (0.0.0.0 binds to all)
maxexpiry=3600 ; Max length of incoming registration we allow
defaultexpiry=120 ; Default length of incoming/outoing registration
disallow=all ; First disallow all codecs
allow=ulaw
allow=alaw ; Allow codecs in order of preference
relaxdtmf=yes ; Relax dtmf handling
rtptimeout=60 ; Terminate call if 60 seconds of no RTP activity
rtpholdtimeout=300 ; Terminate call if 300 seconds of no RTP activity
nat=no ; Global NAT settings (Affects all peers and users)
; yes = Always ignore info and assume NAT
; no = Use NAT mode only according to RFC3581

[200]
type=friend
username=200
secret=200
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[201]
type=friend
username=201
secret=201
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[202]
type=friend
username=202
secret=202
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[203]
type=friend
username=203
secret=203
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[204]
type=friend
username=204
secret=204
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[205]
type=friend
username=205
secret=205
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[206]
type=friend
username=206
secret=206
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[207]
type=friend
username=207
secret=207
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[208]
type=friend
username=208
secret=208
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[209]
type=friend
username=209
secret=209
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[221]
type=friend
username=221
secret=221
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[222]
type=friend
username=222
secret=222
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[223]
type=friend
username=223
secret=223
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[224]
type=friend
username=224
secret=224
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[331]
type=friend
username=331
secret=331
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes

[332]
type=friend
username=332
secret=332
host=dynamic
nat=no
canreinvite=yes
dtmfmode=RFC2833
disallow=all
allow=ulaw
allow=alaw
qualify=yes