I solved this problem. RC maybe local host file. When I use the real DNS name which is registered in DNS server instead of adding entry in hosts file, X-Lite can register in SIP server.

1. Brekeke Product Name and version: Brekeke SIP server 2.1.6.6/239 2. Java version: Java 6 update 3 3. OS type and the version: Windows XP Professional SP2 4. UA (phone), gateway or other hardware/software involved: X-Lite 3.0 5. network pattern Pattern 4 6. Your problem: SIP server side: Linksys ...