At 08:19 AM 21/11/2008, you wrote:

>We are having trouble with a customer's site that is having trouble
>receiving Firebird connections over the Internet. The machine/app
>making the connection to the database can connect to other
>servers/sites just fine. The server in question (actually two
>different servers at the same site) can receive connections from
>within the LAN just fine. Also, a port scan from the client site
>shows that port 3050 is open. They are running FB 1.0.
>
>However, if a connection is attempted to either of the servers from a
>remote site over the Internet, the client machine gets the following
>error:
>
>ISC ERROR CODE:335544721
>ISC ERROR MESSAGE:
>Unable to complete network request to host "xxx.xxx.xxx.xxx".
>Failed to establish a connection.
>The system could not find the environment option that was entered.
>(I removed the IP address above for our client's privacy)

The first message comes from Firebird; the second one comes from the network operating system. Firebird doesn't try to interpret network messages; it merely reports them. That's a generic message that means "The network request doesn't match up with what I'm configured to do."

>Since the servers can receive connections from within the LAN, it does
>not seem to be an issue with the server machines themselves.

Check
1) the subnet mask of the TCP/IP configuration on the server's NIC and the router's NIC (ideally the server's NIC should be local and the router's should be just broad enough to enable access to clients from the private WAN)
2) that the IP address the remote clients are connecting to is a public address. Certain ranges of IP addresses are not.

btw, I am NOT a network boffin. Those are the two things I look at first and fixing them will often resolve it, without my knowing precisely why...

>The site in question uses HughesNet satellite Internet, with a HN9000
>satellite modem. We removed their router from the equation, and
>hooked the server up directly to the satellite modem, and we get the
>same error. The satellite modem does NOT have a built in firewall,
>and has no user-accessible settings on it. We do have other customers
>using HughesNet without this problem.

It's quite likely the original installation was a default one, done at a point where the person doing the install didn't know whether they would need to configure the router for WAN access or not and took a safe option.

>Help!!!!!!

Most providers have guidebooks that you can download for configuring their routers and the nodes on your network. The best ones have an online FAQ where you will often find a description of your exact problem *and* the solution. It's likely that the router's local IP address (often 10.1.1.1) will give you a complicated-looking menu of configuration options, including the NAT policy for resolving public IP addresses to private nodes. If you're lucky, there will be utilities you can call to test it. (Apologies if you have already gone there and done that!)

And don't overlook the risks from allowing external access to database servers...there are safer ways than making connections over the open Internet.

./heLen