Can I run 600ft of 100BaseT?
April 16, 2007 6:59 AM   Subscribe

Can I run ~300ft of ethernet cable from my modem to my router, and then another ~300ft of ethernet cable to a computer, without degrading my connection to the internet?
posted by subpixel to Technology (14 answers total)
You're cutting it close to the limits. If you're using unshielded cable you run the risk of signal interference between devices causing problems.
posted by Blazecock Pileon at 7:12 AM on April 16, 2007

In contrast 100BASE-TX and 1000BASE-T both require a minimum of Category 5 cable and specify a maximum cable length of 100 meters.
So I guess you *might* just get away with it.
posted by snap, crackle and pop at 7:15 AM on April 16, 2007

Should not be a problem. The maximum cable length between any two nodes in a one-repeater 100BaseT network is 310 meters (about 1000 feet). The maximum cable length for CAT 5 patch or crossover cables is 100m (328 feet).
posted by three blind mice at 7:19 AM on April 16, 2007 [1 favorite]

Yeah, thats fine. You get 100 meters (328ft) per run. You just don't want to run it past more than four connections. You currently have two.

If your setup is near 100 meters or more, you should consider breaking up the run to the computer with a switch about halfway through.

Is your modem able to deliver speeds past 10mbps? If not you should set the connection between the modem and the router to 10, not 100.
posted by damn dirty ape at 7:23 AM on April 16, 2007

I ran my connection with 100 feet of cat5 to the router (6 feet to the modem) for many years, with no problem.

Now I'm using about 40' to the router, and my net connection feels a bit snappier, on the order of micro or nanoseconds. So the attentuation difference exists, but is slight.

Unless you absolutely, positively need a low-attenuation signal, you should be fine.
posted by Gordion Knott at 7:27 AM on April 16, 2007

it is within spec ... just make sure that you use cat5 or above ... J
posted by jannw at 7:36 AM on April 16, 2007

You should be fine as long as you are using cat5 or cat5e cable. Cat6 is fine too, but probably not worth the extra cost.

If you don't regularly build cables for a data center (in which case you probably wouldn't be asking this question), either buy pre-made cables, or have a professional put the ends on. Getting the final half-twist exactly right isn't easy, but it may make a difference on such a long run.

If cost isn't a factor, and the total run is well protected, you might consider running single-mode fiber for the entire 600 feet, and moving your router closer to your computers. This will be more expensive, and the cable will be more fragile, but a single mode fiber pair can carry signals up to at least 40 Gbis/sec.
posted by b1tr0t at 7:42 AM on April 16, 2007

Wired Ethernet isn't like wireless: cable losses increase linearly with distance, not with the square of distance as wireless approximately does. It doesn't ramp its speed down little by little to preserve something approaching an acceptable error rate like wireless does, either; a 10/100 device will occasionally decide to work at 10 if the cable is too noisy/lossy to be workable at 100mbps, but this is more of an accidental safety net than an actual design feature.

If you do drop the link speed to 10mbps, you'll probably find you can easily push 100mbps-capable equipment a fair way past the official cable length spec.

OTOH, if there's more than one computer hanging off your router, and you want them to be able to talk amongst themselves at speed, you'd want a 100mpbs link at least between the router and each computer.

Any modem that won't go faster than 10mpbs will probably only have a 10mpbs Ethernet port on it anyway.

If you're actually thinking about installing 200m of cable in some kind of semi-permanent way - maybe in walls, or in a trench - you should probably spend a few extra bucks and do the whole lot with a single run of fiber, with a 100base-T to 100base-FX converter at each end. Fiber has essentially unlimited bandwidth, and replacing a couple of converters is generally going to be easier than rewiring.
posted by flabdablet at 7:45 AM on April 16, 2007

jinx :-)
posted by flabdablet at 7:45 AM on April 16, 2007

Single-mode fiber is overkill for this kind of distance, BTW; multi-mode should work just fine and is way cheaper to deal with.
posted by flabdablet at 7:50 AM on April 16, 2007

Nth'ing the fact that this is well within spec, and there should be no loss when using CAT5/5E cabling.

Anecdotally, I have run Ethernet at over 600 ft on Cat3 cable (well outside of the spec), but it is not recommended.
posted by stovenator at 8:37 AM on April 16, 2007

Isn't handshake timeouts one limiting factor on cable lengths? If the cable is too long, latency causes handshakes to fail. If you push it too close to the limit, you'll get a higher rate of retries.
posted by Steven C. Den Beste at 9:28 AM on April 16, 2007

Steven, AFAIK the only Ethernet handshake stuff for which cable length is a factor is part of the collision detection mechanism, and if you're using 10/100base-T point-to-point links between switch or router ports (as opposed to hubs) and running full duplex as you should be, there are no collisions to detect.
posted by flabdablet at 9:37 AM on April 16, 2007

The handshake stuff to worry about is negotiating the duplex and speed with 10BaseT/100BaseT. At distance this fails, but can be overcome by explicitly setting the duplex to full and selecting either 10BaseT or 100BaseT on one side or the other (or both, making sure they match). Allowing these to be set to Automatic can result in failures at distances.
posted by stovenator at 9:41 AM on April 16, 2007

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