cable modem to wireless router troubleshooting
June 21, 2015 5:23 PM   Subscribe

I've got a Arris SB6141 cable modem. When I hardline into it, I get over 100 Mbps down and about 20 Mbps up. When I connect it to a Linksys N-Ultra WRT160N broadband router, I get 0.5 Mbps down and 12 (?!) Mbps up. What gives, and how can I get more speed through my router?
posted by the man of twists and turns to Technology (9 answers total)
Response by poster: The neighbors are all mostly on channel 1, 6 and 11, with most of the power on 1 and 6. I don't need a lot of range.
posted by the man of twists and turns at 5:25 PM on June 21, 2015

I would:

1. Call your cable provider and ask them

2. Try a different router and see if that makes a difference

3. Try a different computer..

Narrow it down to where the problem lies.....
posted by HuronBob at 5:34 PM on June 21, 2015 [2 favorites]

There are really only 4 distinct (non-overlapping) wireless channels in the 2.4 GHz band - 1, 6, 11, and 14. Channel 14 is illegal to use in the United States, so most routers disable it by default. You very well might have enough contention on use of the 2.4 GHz band to reduce throughput to what you see.

Consider switching to the 5 GHz band, which is significantly less congested (most people don't even know it's available for use).
posted by saeculorum at 5:35 PM on June 21, 2015

What happens if you connect via ethernet (instead of wireless) to the router? If that's slow, then something's definitely wrong with the router.

If it's just the wireless, then it sounds like you've either got the router in a location where it can't broadcast well (e.g. too many walls in the way), or there's too much congestion from your neighbors. If it's the former, try moving the router closer to the devices. If it's the latter, it's probably time to invest in a dual-band router that can use the less-crowded 5GHz spectrum. You might also want to look for a router that has external antennae, as that can also help with reception issues.
posted by Aleyn at 7:18 PM on June 21, 2015 [1 favorite]

If you have an Android phone, download WiFi Analyzer which will read your local WiFi situation and tell you what channel is "most clear".
posted by kschang at 10:27 PM on June 21, 2015 [1 favorite]

Best answer: There's no way that just being on the same channel is causing THAT terrible of performance. I would work at like, 10mbps, not 0.5. Everyone is kind of barking up the wrong tree with that one.

Have you done a serious hard reset of the router, installed the latest official firmware, then reset it again?

Have you tried out another router or access point in the same location?(seriously even just buy one from best buy, try it out, and return it).

I've used both that modem and that router(although not as a pair). It's a bulletproof router, and was used as a stand-in AP in an office i adminned for quite a while.(while we waited for the real, replacement AP)

My guesses would be:

1. Some buried setting at a silly/incompatible with real life position.

2. Something screwy in the router config, possibly some kind of weird corruption behind the scenes that isn't even exposed by the settings.

3. firmware glitch, which is why i'd suggest verifying you're running the latest version(i've had routers that would get like this after X amount of time consistently, or instantly, but were fine after a firmware upgrade or downgrade)

4. EMI/RF interference very close to the router. A shitty power supply, a tiny arc in something, shielding being screwy on something, some junky ass old piece of equipment. Even a junky laptop/router/AV equipment power brick or internal supply could be spitting out garbage

5. hardware failure in the router in some way.

I'd get to 3 and do it all at once by updating the firmware and wiping. Then i'd install dd-wrt and continue forward from there. After i had tested the router at say, a friends house across town, i'd either decide to explore #4 or slam dunk the thing in the garbage and buy like... this(oh my GOD that has gotten cheap since i last had to link one).

Having been around this loop a million times both in professional and casual settings though, i'd have already ordered the new router before i even started troubleshooting this one. You can always return it, and i'd bet money the problem is with the router, not the environment.

802.11n is remarkably good at avoiding collisions and playing nice with other networks or interference. Only really glitchy, junky, or dying routers stumble this hard. Every time in recent memory i've found myself going "oh, it MUST be interference!" it was actually just the router/AP being a hunk of garbage, and a new unit "magically" performed fine with the same congested airspace.
posted by emptythought at 3:32 AM on June 22, 2015 [4 favorites]

I'm 100% in agreement with emptythought that it's a bad router. If it were interference, it wouldn't be quite so bad, nor quite so consistent - your speeds would vary more wildly, depending on where you stood, where your pets were laying, how many active sunspots there were, etc.

I had a similar device that I fought with for far too long - it had excellent wired connectivity, but the wireless throughput maxed out at about 1 mb/s. The issue survived multiple factory resets, nvram resets, and eventually a new firmware. So I eventually concluded that it had to be a bad interface on the router.

So do yourself a favor, and get a new router. Preferably one with dual-channel N. The 5ghz range really is very nice. I'm currently a big fan of the ASUS RT-N66U. That N53 that emptythought links is also nice, if you're looking for <$100.
posted by god hates math at 3:56 AM on June 22, 2015 [1 favorite]

Hmmm... This is a cable modem, NOT a combo modem/router. So it can't be double-NAT.

The ONLY other thing that makes sense is the RJ-45 cable is NOT feeding 100 Mbps (or 1Gbps) to the router. I'd check the cable that link the two first. (Put a laptop on it?) Then if that doesn't resolve it, try a different router.
posted by kschang at 11:05 AM on June 22, 2015

Reading OP's description of the steps s/he's already taken, it's not clear whether they have already tried plugging in via Ethernet to the router.

There are really three cases that need to be tested, two of which OP has already tried, but I am not clear which two exactly:
  1. Connect a computer directly to the cable modem (not the router) with an Ethernet cable, so that it gets an IP address assigned by the cable company; I think this is what OP tried and got 100+MB down on.
  2. Connect a computer directly, via Ethernet, to one of the LAN ports on the back of the Linksys router, after connecting it up to the cable modem and allowing it to establish a connection.
  3. Connect a computer to the Linksys via some flavor of wireless, probably 802.11n.
Whichever of these tests hasn't been performed yet, should be.

If #1 worked well, but #3 failed, then #2 will establish whether the problem is in the gateway/router part of the Linksys, or if it's in the wireless access point or RF side, which could indicate a problem with interference.

If test #2 is fast, then I'd start thinking that interference is likely, and I'd start playing with moving the AP around, moving the antennas, looking for other sources of 2.4GHz, etc. (In my experience the real culprits when it comes to poor WiFi isn't a surplus of other access points, it's older 2.4GHz gear, particularly cordless phones and wireless speakers. I have a Sharper Image "Direct Sequence Spread Spectrum" speaker system that will absolutely annihilate WiFi in an entire house when it's turned on.)

But if #2 indicates a slow connection as well, then the problem isn't with the wireless side, the problem is in the router portion of the Linksys. I'd do a factory reset and reconfigure it from there, figuring maybe something got messed up with its QoS settings or something. If that doesn't work I'd replace it and see what happens again.
posted by Kadin2048 at 4:01 PM on June 22, 2015 [1 favorite]

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