Strange dialing

Several things:
1.- Regarding the /tmp directory I see jetty-0.0.0.0 directories, hsperfdata_asterisk and hsperfdata_root directories. Are they safe?
2.- I have set the dial patterns that all long distance call go out the VOIP line from sipstation. Now the long distance calls all work. The local numbers go through a dahdi connection to a land line and they still act up. We have two dahdi external lines, and they act the same. But when I use the VOIP connection for calls, it works fine. I'm sure there is a dahdi configuration problem!
3.- Could I have some pointers on how to tighten the firewall. I have forwarded port 5060 and ports 10000-20000 to the SIP server. We go through two routers from the Internet to our dedicated voip subnet. Otherwise there is no other connection. We have no external SIP phones other that our VOIP provider which is SIP Station. What I need to know is what range of IP addresses to allow, and otherwise no other IP addresses allowed. I suppose iptables would be the way to do this once I know what IP addresses to allow.
James