I found an interesting link for my arcor-cell-pipe modem 100 in german language.
There is information how to telnet to the modem, how to get the firmware and other internas, not mentioned by Arcor.
If I understood right, you may even activate routing.

http://modemhilfe.de.vu/
other menntioned modems are
- Xavi 7000
- Xavi 7001
- Teledat 331
but I didn't look closer at them.

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don't visit my homepage:http://home/arcor.de/hirnstrom/