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Posted on 1999-07-13
Medium Priority
Last Modified: 2013-12-27
Hi, i have a lanmodem from 3com, and i was wondering what the hek is wrong with it ? I recently posted a question here because i couldnt connect to any ftps other than port 21, and i used pasv mode and it was fine. NOW, i can connect to SOME of them, like i cant connect to an ftp on port 1998, and an ftp on port 80. Why does this happen ? Im so sick of it, im ready to go back to my regular modem, is their some kind of special settign or software that i can use ? Please help. Thanks
Question by:jokerjoker
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LVL 12

Expert Comment

ID: 1150198
It's probably *NOT* the fault of your modem.
TCP/IP carries your request to the remote computer,
and then "knocks" on the "door" labelled '21' or '1998' or '80'.
If there is nobody "listening" for the "knock",
you will get a "time-out" message.
If there's a burly security-officer at that door,
you will get a "connection-refused" message.

Another possibility is a security-officer on your LAN,
who is reading each message as it passes by him/her,
and is intercepting each of your attempts to use
a "non-standard" door ('21' is the "standard-door".)

Changing modems will make *NO* difference,
unless the change in modems implies that you
are bypassing the LAN-cop, and connecting
to a different ISP.

Author Comment

ID: 1150199
This told me nothing on how to solve the problem.

Expert Comment

ID: 1150200
Take a look at

and more specific at the part of configuration regarding applications.

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LVL 12

Accepted Solution

Otta earned 800 total points
ID: 1150201
> This told me nothing on how to solve the problem.

It's probably *NOT* the fault of your modem,
since your modem works.  Instead, ask your LAN-administrator
and/or Computer Security Officer about any "firewalls"
or "IP-packet-filtering" which is in effect.
When you use your old modem, you are bypassing any such items, so that's why it works.


Expert Comment

ID: 1150202
A 3com lanmodem is a modem integrated with a router / proxy server / multi-host address translator.  You connect this device on a typical network, and everybody can instantly surf the internet on 1 normal internet user account.

This mechanism imposes some limits on the traffic that is being transported.  It will not be as tranparant for various protocols as a normal modem with Windows DUN directly connected to the ISP.

What needs to be done is to check what protocols / ports /adresses are being blocked / corrupted, and the to check at the URL i gave with the configuration of the Lanmodem.


Expert Comment

ID: 1150203
Sorry jokerjoker but since i don't know the Lanmodem very good i can not be of any help.  Who administers the device ?  Did you do that yourself ?

I probably would try to re-initialize the Lanmodem, or bring it back to factory defaults and start all over again with configuring the device if that did not help.

Please give us some feedback.   Did you check the URL i gave ?  Was it of any help ?


Expert Comment

ID: 6873003

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