So I'm not as tech-savvy as I thought I was...
August 10, 2015 6:25 PM   Subscribe

Using a new modem/router setup brought on unbearably slow speeds, but which is to blame??

I have three pieces of equipment: a cable modem, a router, and a combo modem/router box. Up until now I've been using the combo box to connect to the internet, and the router in another part of the house as an access point. The modem has been sitting in a drawer. For complicated reasons, I need to switch the setup - I need to use the separate modem and router in order to connect to the internet, and use the combo box as an access point (or get rid of it all together, possibly).

Under the old setup I got respectable speeds - about 5-6 mbps, regardless of whether I was connected to the combo box or the router-as-access-point. However, when I reset everything and plugged the modem and router into the cable and began using them as God intended, my speed fell to about 0.2 mbps. I tried changing the channel in the router but it didn't make a difference.

This setup used to work fine in my old place but it's been a couple years. I suspect there's something wrong with the modem (since the router had been working fine as an access point), but most accounts of faulty modems talk about internet cutting off intermittently, not simply being slow. Or maybe there's some setting I forgot to change that I'm not thinking of? Replacements are somewhat pricey, so I'd rather not shell out for both if I don't have to.
posted by exutima to Computers & Internet (7 answers total) 1 user marked this as a favorite
Response by poster: Note: My computer doesn't have an ethernet port, so I can't just plug directly into the modem and see how it goes.
posted by exutima at 6:29 PM on August 10, 2015

Did you call up your ISP and provide them information on the stand-alone router? Most ISPs will simply not allow strange modems to access the network at all, but yours may just be throttling you. Once you provide them with the router's identifying info, things should speed back up.
posted by falconred at 6:44 PM on August 10, 2015 [1 favorite]

What falconred said, except replace the word "router" with "cable modem".
posted by strangecargo at 6:46 PM on August 10, 2015

Most likely you have accidentally caused a Double NAT.

Check if both the WAN and LAN port are set to DHCP with everything in default.
Reboot both modem and router.

If that doesn't help reset the router to factory settings and follow the setup instructions without making any changes you thing might be "better". You can always mess with that later.

Also check that you did not create a loop back by reconnecting a network cable back into the network therewith creating a loop sending your network in a tailspin.
posted by Mac-Expert at 6:47 PM on August 10, 2015

does your modem have a log? it may have useful error messages there.

(while you might have a double NAT there's no reason that would slow everything down)
posted by andrewcooke at 7:46 PM on August 10, 2015

Double NAT certainly brings a network down to a halt or at least very temperamental. Give it a try ;-)
posted by Mac-Expert at 10:07 PM on August 10, 2015

USB ethernet adapters are $10, and very useful for troubleshooting situations like this. It's going to be much easier to diagnose the problem if you can isolate it to the router or the modem.
posted by Aleyn at 10:55 PM on August 10, 2015 [1 favorite]

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