First, a question:

Do you assign IP addresses on your LAN yourself, or does your cable =

modem act as a DHCP server?

If the former, all you have to do is divide your LAN into two subnets
and set up a static IP routing table on your "router" NetBSD box.  By
*not* routing the AppleTalk traffic, you can isolate your cable modem
and keep it happy.  If you don't set up an atalk routing table on the
router box, atalk traffic won't be forwarded over the router box.

If the latter, you have two choices:

	a) Forward DHCP requests from your Macs to the cable modem.
	b) Run NAT on your router box.

For a starter, read man pages route(8), netstat(1) and some others
referenced from these.

Ken

On Sat, 22 May 1999 15:09:05 -0500, Evan Fletcher wrote:
> Hello.  I have a problem that has bothered me for a good portion of a =

> year and I have not been able to fix.  The story behind it is a =

> little long so please bear with me.
> =

> I have a cable modem and a LAN with four macs (2 running NetBSD). =

> All four macs are connected to a Asant=E9 FriendlyNet Ethernet hub wit=
h =

> the cable modem plugged into the "Uplink" port.  With the cable modem =

> connected, I am unable to have an AppleTalk network.  Without the =

> modem, AppleTalk works fine.  I have discussed this problem with the =

> cable company, but they are too stupid to do anything about it. =

> (They have even asked me for mac help in the past.)  The ultimate =

> problem is that I am unable to share files easily and most =

> importantly, I am unable to network my printer without AppleTalk.
> =

> So where does this involve NetBSD you ask?  One of my IIci's (NetBSD =

> 1.3.3 -- haven't had enough time to upgrade to 1.4) has two ethernet =

> cards.  I would like this to act as a gateway for three machines and =

> allow TCP/IP traffic to pass on through the cable modem and AppleTalk =

> packets to be blocked from the cable modem, hopefully allowing an =

> AppleTalk network to be formed among the two MacOS computers and the =

> printer.  Unfortunately for me, I have been unable to figure out how =

> to accomplish this task.  I thought routed might work, but I can't =

> figure out how to configure that.  I have also looked at gated, but I =

> have no idea if that will work either.  I have turned on ipfilter in =

> /etc/rc.conf, and this has allowed me to set this computer as the =

> "router address" in the TCP/IP CDEV, but the computer only utilizes =

> ae0, instead of both ae0 and ae1.  This ASCII diagram might help =

> describe what I need.
> =

> =

> LAN --->  HUB ---> [NetBSD ae0] ---> [some software] ---> [NetBSD =

> ae1] ---> [cable modem]
> =

> *It is important to note that I do not need NAT, since the cable =

> company doesn't care (or seem to notice) how many IP addresses I use.
> =

> I am still learning unix and I am unable to find adequate =

> documentation to assist me in configuring the computers to do the =

> tasks that I require.  Please help me figure this out.
> =

> Thanks in advance,
> Evan Fletcher
> --
> Evan Fletcher
> <evan@router.ecmhs.org>
> =