I just built this home wireless network with a Linksys WRT54GL router and a Motorola SBG900 Wireless Cable Modem Gateway (which by itself is a modem as well as a router, but I just wanted to use it as modem). I chose the lowest level of firewall at SBG900 and the default firewall settings for WRT54GL. That was when I couldn't ssh to a remote server. But when I turn off the firewall at SBG900, I can finally ssh to the remote.
So I just wonder if firewall is commonly available in most of today's modems (not only the modem and router things)? Is it safe enough to just have the default firewall of WRT54GL without any from SBG900? Like what I did to enable ssh to the outside? What settings in router and modem could possibly disable ssh to the remote?
For WRT54GL, by default, Block Anonymous Internet Requests, Filter Multicasting and Filter IDENT (Port 113) are enabled, but Filter Internet NAT Redirection is not.
For SBG900, I cannot find the details of what does each level of firewall does in its specifications.
Thanks and regards!