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I setup Trixbox on one PC (192.168.133.2) this worked fine for internal and VOIP etc. I just couldnt get the Digium BRI card working so they suggested I move away from Trixbox and use Fedora and Asterisk and install and compile myself. I have done that on a new machine (192.168.133.3).
I am now testing it with my first SIP client. I have not managed to get it to connect at all yet.
I have a default installation with the sample config files and have only modified the two below. Here is the total contents of both.
I have tested X-Lite from my PC - it connects to trixbox OK on 192.168.133.2 but not my new self built asterisk server on 192.168.133.3

[root@Aster2 asterisk]# cat sip.conf
[general]
port=5060
bindaddr=192.168.133.3
context=default
srvlookup=yes

[Guy]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[Barbara]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[Pasqui]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[Maureen]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[NewGirl]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[Packing]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[Showroom]
type=friend
secret=bongo
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=tinwareinternal
call-limit=4

[root@Aster2 asterisk]#


Not sure this is relevant but its the only other file apart from misdn stuff that i have touched yet.

[root@Aster2 asterisk]# cat extensions.conf
[general]

[tinwareinternal]
exten => 200,1,Dial(SIP/Guy,,r)
exten => 201,1,Dial(SIP/Pasqui,,r)
exten => 202,1,Dial(SIP/Barbara,,r)
exten => 203,1,Dial(SIP/Maureen,,r)
exten => 204,1,Dial(SIP/NewGirl,,r)
exten => 205,1,Dial(SIP/Packing,,r)
exten => 206,1,Dial(SIP/Showroom,,r)

[root@Aster2 asterisk]#


Asterisk is running 
[root@Aster2 asterisk]# ps aux | grep asterisk
root      4231  0.0  1.5  42860  7668 ?        Ssl  00:27   0:00 asterisk
root      4362  0.0  0.1   4008   704 pts/0    S+   01:12   0:00 grep asterisk
[root@Aster2 asterisk]#


My X-Lite client just says discovering network and then:
Registration error: 408 - Request Timeout