Robert Redelmeier <redelm@ev1.net.invalid> wrote:
> In comp.dcom.lans.ethernet ps56k <pschuman_no_spam_me@interserv.com> wrote in part:
>> "Rick Jones" <rick.jones2@hp.com> wrote in message
>>>J <kmclaurin1959@gmail.com> wrote:
(snip)
>>>> Can I put a switch between the cable modem and the router?
>>>> I tried it with a hub I had laying around, and it didn't work.
>>>> Would a switch do the job?
>>> Probably not. Your "router" is the device fronting for your systems
>>> with the cable modem. If you want your systems to speak-out the cable
>>> modem, they need to go through the "router."
(snip)
>> As mentioned - it won't work - because your "local network"
>> is created by your router.... your IP address is coming from it,
>> along with some general protection from the outside world.
This is, at this point, a TCP/IP question which should probably
go to comp.lans.protocols.tcp-ip.
(snip)
> As the above replies have mentioned, neither hub nor switch
> will work. You are relying upon the router to do NAT so you can
> share the connection. It also has established the internet login.
> At the very least you would need to configure the vampire machine
> with your WAN IP, gateway and DNS. If the cablemodem will even
> listen to two different MACs.
> Since you have the long wire run, you can use it for the backhaul.
> Standard Cat5 cable has 4 pairs and only needs two for 10baseT
> (normal for modems) or 100baseTX (normal LAN) . This is not exactly
> per standards, but I have never seen it fail when correctly wired
> (no split pairs).
As long as he doesn't upgrade to gigabit. I believe we are getting
close to NAT routers supporting gigabit for the LAN ports.
Maybe not so much longer before they can route gigabit.
I have my wireless net routed off the wired net, so I can get full
speed through it.
(snip)
> I have not seen these splitters commercially offered, but
> they are easy to make with 3 jacks in a surface mount box.
> Just punchdown some cross-connect in the right pattern.
I believe that they are commerically sold, but more expensive
than many small fast ethernet switches. (Try
www.blackbox.com)
You could also attach two plugs onto the end of a cable with
a crimp tool. It would be a little sensitive to strain from
being pulled on, though.
Another way that could work is to put a small ethernet switch
at both end of the long cable. As the wireless NAT routers
usually have a four port switch, you could even use that if there
were two ports available. The result would be that both the WAN
side and LAN side nets would be on the long cable. A few things
have to work right to make this work. The cable modem has to
assign the IP address to the router (usually DHCP). That means
that the router likely has to power up first. Most, I believe,
are programmed to assign only one address. That would work best
if the NAT router could have a specific MAC address assigned.
Otherwise, one has to be careful that the NAT router DHCP doesn't
assign the address itself.
OK, I don't recommend that method. While running two IP nets
on the same ethernet should not be a problem, it requires too
many things to work just right. If the WAN address was statically
assigned it should work, though, if the NAT router doesn't have
the ability to assign a specific MAC address. It would also work
with MAC address filtering on the LAN side, but that is a lot
of work to get right.
Managed switches that could assign specific MAC addresses to
specific ports should also work, but those are pretty expensive.
-- glen
Re: Putting a switch between router and cable modem 
Linear Mode
