amanda won't work through firewalls unless the package is configured at build time with the following options: --with-portrange=xxx,yyy --with-udpportrange=xxx,yyy
Well, you really want to use --withtcpportrange=aaa,bbb --with-udpportrange=ccc,ddd, and selet the values of aaa,bbb,ccc and ddd that are large enough to back up your enterprise, but not so large as to make the firewall administrator whimper. Oh, and you need to build all of your Amanda clients with set of portranges that you use on your server. The real solution would be for the portranges to be configured in the amanda.conf file on the server. This enhancement is somewhere on my very long list of "things to do some day".