Problem in asterisk with sip

hi ,

I am facing some problem from few days .
After successfully installing asterisk when i try to make call using sip than call is not landed , it just show calling… on sip
phone .and than request timeout . i can’t understand why so plz help me .
I am also give u my system configuration detail .

machine OS/Kernel:-- Linux RedHat version 4./ 2.6.9-22.ELsmp
Intel Xeon Dual x86_64 processor.

asterisk package version

LibPri – libpri-1.2.4
zaptel-- zaptel-1.2.10
asterisk – asterisk-1.2.13

extension.conf
[test]
exten=>1209,1,Answer()
exten=>1209,2,SayNumber(12345)
exten=>1209,3,Hangup()

     sip.conf
     [test]
     type=friend
     username=test
     secret=test
     host=dynamic
     context=test
     allow=all
     callerid=test

Plz help me … I am waiting for ur response.
thanx in advance
Rashid