Does a 3Com ISDN LAN modem need a separate firewall?

Does a 3Com ISDN LAN modem need a separate firewall?

Post by Adam Lipsc » Sat, 18 Oct 2003 00:58:27


Currently I connect my home office LAN to Freeserve via ICS and BT Home
Highway. The ICS host machine has a ZoneAlarm firewall to protect the

But I find ICS a bit flaky - usually its OK but can go AWOL leaving the
client machines unable to connect. This happens often enough to make it a

I am thinking getting a 3Com ISDN LAN modem - an ISDN TA with 4 ethernet
ports. It has NAT etc to hide the LAN machines IP addresses.

Do I need a firewall as well or can I get good protection from configuring
the TA?
What are the issues to consider?

TIA - Adam

Does a 3Com ISDN LAN modem need a separate firewall?

Post by wdg » Sat, 18 Oct 2003 07:56:56

Even *with* a firewall product (such as Zone Alarm) the config interface
of your ISDN Lan Modem is still "exposed". Anyone who has knowledge of
your ISDN telephone number could call into it and hack your setup config.
The chances of this occurring are small, however. To protect against this
threat make sure that you set a configuration password in the GUI

NAT does provide a modicum of protection but I would still advise use of a
software firewall, i.e., Zone Alarm. Alternatively, if you're using
Windows XP, you can enable Windows XP's built-in firewall. I know this is
an available option in XP Pro and I believe it's available for user
install as an option in Home Edition but you'll need the original
distribution disk. Might be easier to just get Zone Alarm (the free
version, not PRO. Zone Alarm Pro reportedly has some problems w/XP.

If you get the LANModem be sure to check out my "Telnet Interface" page.
You'll find a lot of useful info there about your LanModem that you won't
be able to find in any of 3Com's product documention. Check it out here:
< ~wdg/oclm.html>

In article <bmmf76$5o3$ XXXX@XXXXX.COM > "Adam Lipscombe"
< XXXX@XXXXX.COM > writes:


Does a 3Com ISDN LAN modem need a separate firewall?

Post by hudsonasmi » Sat, 18 Oct 2003 08:35:56

I have the 3Com ISDN Office Connect Lan Modem. I have visited
internet sites that offer to check the security of my setup, and have
dones so. All reports that I have gotten back say that my system is
not vulnerable.

Keep in mind the other poster's message about setting password for
configuration. I have done that.

I also do not leave the computer "connected" all the time.

I have never had any problems with this in the two years that I have
been using ISDN.

On Thu, 16 Oct 2003 16:58:27 +0100, "Adam Lipscombe"