Zoiper and egika don't work with asterisk

I have just start working with asterisk. and I installed the 11 version in ubuntu 12.04.
The installation went very good. But when I wanna use it with a soft phone like zoiper and egika, asterisk don’t see any user I configure in these softphone.
When I make “sip show peers”, it always show :

Name/username Host Dyn Forcerport ACL Port Status Description
bureau/bureau (Unspecified) D 0 UNKNOWN
1 sip peers [Monitored: 0 online, 1 offline Unmonitored: 0 online, 0 offline]

My sip.conf is :

qualify=yes ; Qualify peer is not more than 2000 mS away
nat=no ; This phone is not natted
canreinvite=no ; Asterisk by default tries to redirect
port=5061 ; Uncomment this line if Ekiga and Asterisk are on the same host

my extensions.conf is:
exten => 12,1,Dial(SIP/bureau)

I don’t know if my .conf files has problems or my installation has problems.
for information I have installed zoiper in the same computer as asterisk and Egika in a windows computer.
Any help please.

Did you change the local port numbers on the phones (to 5061)?

If so, what appears on the Asterisk CLI when they try to register?

Especially if nothing, what appears on the sip set debug on output when they try to register?

If nothing, what does a packet sniffer (tcpdump, wireshark, etc.) say when they try to register.

PS there is no such word as “wanna” in the English language, or at least not in common use. It is a slang term that foreign speakers should try not to learn. It’s a contraction of “want to”, although “would like to” is normally more polite. The other English errors are reasonable for a foreign learner.