Question : Ping: Destination Port Unreachable

3 PC's connected to Internet thru Linksys Cable Router/Switch.  Static LAN IP's.  (Some port forwarding being run)  Used to be able to run a small application that ftp'ed out to a host server & transferred image data.  Suddenly, one day, it stopped.  The application tells me "Network Disconnected," which doesn't tell me much, only that that's what the programmer decided to use as an error message for God knows what problem.  I open a dos prompt and ping the server, and get four tidy replies from the translated IP ending with "Destination Port Unreachable."  -Same result from any of my local machines.  One must have a 'user account' at this particular server/service, and I do have one.  I can log in from their web front-end and manage my account.  I even created a brand new account & tried the new account with the applet -same problem.  I believe it's network.  I have spoken with other users of the service and they are able to ping the server, and their transfer application works fine.

I am prepared to e-mail them for support, but, like I said, I believe it's a networking issue.  I looked up my error, and you folks came up as a search result.  I like what I see here.  I wonder if I started suffering from an MTU issue.  -But why, all of a sudden?  I know for a fact that the server handles the image data transfers on ports 8570 & 8571, as opposed to the typical 20/21.  But my system always handled it, and nothing has changed in my config.  I also wondered if my 3-com sharkfin Cable modem could be the culprit.

If anyone has anything to offer, I appreciate it.  I am going to e-mail them tonight, and if I hear a solution, I'll post it here.

PS, I can't determine if this is an easy or hard question.  It's hard as hell for me, but for one of y'all, it may be quite simple.  I'm choosing 50 because I'm new and only have 75 points.

JW

Answer : Ping: Destination Port Unreachable

>I really don't know where I got the IP from, the Cable
>Modem, or my ISP.  I understand the cable modem does
>DHCP/hand out IP's, but, if that's the case, how did the
>CM get more than one IP from my ISP?  -And, if the IP
>came from my ISP based on the 'new MAC,' I thought the
>MAC at the CM had to be registered w/ my ISP, in order to
>get an IP -when the new MAC came in, it should have been
>rejected?

Most CM's I've seen function as a bridge - the CM gets an IP (usually within RFC1918 space) from the ISP (probably based on it's own MAC addr), and then everything else is up to you - the MAC addr from your router (or workstation) should be passed on to the equipment at the ISP (since the CM is bridging), and so the ISP should notice/respond to a change in your local MAC addr.  

I'm fairly certain my own cable ISP does domething like this - if you run a sniffer directly on the router (so you can see WAN traffic), you are constantly barraged by ARP requests for other machines on the same node (which to me would indicate that my CM is acting as a bridge).

>I hope my adventures help someone else, that's all I have to say

That's what EE is all about - glad you could contribute!

Cheers,
-Jon