LinuxQuestions.org - Suse firewall and asterisk

Hi, I quite new to linux suse 9. I wanted to implement some firewall setting on my sip server. The problem is that i don't know we to start. I'm thinking that if I implement such thing would block the connection(sip) to my other server/partners in other country. I have a boogey last time. How can I implement the firewall without affecting the asterisk,sip connection to other servers. How can I also allow a sshd connection to certain IP address.Here is what I've got the on the logs.

Nov 16 05:54:10 ss7box sshd[5496]: Failed password for illegal user magenta from ::ffff:61.43.153.30 port 46497 ssh2
Nov 16 05:54:11 ss7box sshd[5498]: Illegal user magenta from ::ffff:61.43.153.30
Nov 16 05:54:11 ss7box sshd[5498]: error: Could not get shadow information for NOUSER
Nov 16 05:54:11 ss7box sshd[5498]: Failed password for illegal user magenta from ::ffff:61.43.153.30 port 46571 ssh2
Nov 16 05:54:12 ss7box sshd[5500]: Illegal user maroon from ::ffff:61.43.153.30
Nov 16 05:54:12 ss7box sshd[5500]: error: Could not get shadow information for NOUSER
Nov 16 05:54:12 ss7box sshd[5500]: Failed password for illegal user maroon from ::ffff:61.43.153.30 port 46639 ssh2
Nov 16 05:54:13 ss7box sshd[5502]: Illegal user maroon from ::ffff:61.43.153.30
Nov 16 05:54:13 ss7box sshd[5502]: error: Could not get shadow information for NOUSER

Please help me on this one. Thank you very much in advance