Putting a switch between router and cable modem

Hello, Here is my current config (downstairs in my basement) :

Coax cable into cable modem (this is the only cable access I have in my house) Ethernet cable from cable modem into Linksys 4 port wireless router WAN port

2 computers plugged into ethernet ports on the router (1 from a long cable run from upstairs) Wireless access for 1 laptop

The wireless access is poor upstairs in my house. I'd like to move the wireless router upstairs. I have done this, connecting the the ethernet cable with the long cable run from the WAN port on the router directly to the cable modem downstairs. The problem is I now don't have the router downstairs to plug my downstairs computer directly into.

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?

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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."

If you have poor wireless upstairs when the "router" is downstairs, but need wired connections downstairs, you might consider placing an "access point" (eg the WRT54GAP) upstairs, running the long cable you used for your wireless "router" to connect the access point to the router. (or connect your switch/hub to the router and then the access point to the switch if you need wired connections upstairs as well).

rick jones

Reply to
Rick Jones

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.

Common answer is the additional wired WAP at the other location.

Another common option is to place the router/wap where you need wifi, and try using inhouse AC powerline networking to backhaul to your "wired" desktop. We use this for our Xbox and Tivo in the family room, with the WAP upstairs.

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In comp.dcom.lans.ethernet ps56k wrote in part:

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).

It would look like this: cablemodem in the basement, plugged into a splitter (A-side) plugged into the Cat5 to upstairs. There it plugs into another splitter, and out the A-side into the router. One port from the LAN-side of the router is plugged into the B-side of the splitter where it is sent through the same cable back downstairs where the downstairs computer is patched into the splitter B-side.

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.

-- Robert

Reply to
Robert Redelmeier




This is, at this point, a TCP/IP question which should probably go to comp.lans.protocols.tcp-ip. (snip)

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 believe that they are commerically sold, but more expensive than many small fast ethernet switches. (Try

formatting link

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

Reply to
glen herrmannsfeldt

Robert Redelmeier wrote: (snip)


I thought blackbox had them, but this seems to be where one.

formatting link
They are $9.99 each, and you need two. (They should sell them in pairs.) Also, these depend on you having jacks at both ends of the cable, or you need RJ45 inline couplers. Those are $1.79 for the ordinary ones, or $7.99 for the Cat5E rated version. Most likely the $1.79 version will work for 100baseTX and house length cables.

This comes up as a sponsored link on google. I don't have any connection to the company.

-- glen

Reply to
glen herrmannsfeldt

Here's another:

which includes a wiring diagram if you want to make your own. No clue on the price (as I make my own).

More of the same on eBay:

$19 for two including jumpers.

$16 for two without the jumpers.

Be VERY careful in reading the descriptions on eBay. Many of the cheaper "ethernet splitter" items are really parallel "T" connectors, which are not suitable for the purpose.

Reply to
Jeff Liebermann

This one won't work. See below.

Argh. The last item I listed will NOT work. It's for sharing a computer and a POTS phone on the same CAT5 network, not two computers. Both jacks should be wired for pins 1,2,3 and 6.

Reply to
Jeff Liebermann

Apple's AirPort Extreme and Time Capsule products (both of which route wired to wired and wired to wireless) have gigabit ports. Certainly they support gigabit rates on the LAN ports. Steve

Reply to
Steve Fenwick

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