Networking trouble involving two routers.

August 5, 2004 5:50 PM

I need help from network-savvy mefites: I've just moved in to a house with four friends and we're trying to set up a network. Collectively, we have two router/switches with one feeding into another and computers plugged into both. All the computers are receiving an internet signal, but those plugged into the second router/switch can't communicate with those only behind the first and vice versa, making file sharing and iTunes streaming impossible. Is there a way to fix this? I'll try to stick around and give more specific information if needed.
posted by Phatty Lumpkin to Computers & Internet (17 answers total)

turn off dhcp on the second router. it should be functioning simply as a hub.
posted by andrew cooke at 5:57 PM on August 5, 2004

Response by poster: Thanks, I'll try that. BRB
posted by Phatty Lumpkin at 5:58 PM on August 5, 2004

ooops, that's misleading. turning off just dhcp probably isn't enough. you want to turn off nat too. basically, you don't want a router at all, you just want whatever signal comes in from the first box to be copied out to the connected computers (and vice-versa).
posted by andrew cooke at 5:59 PM on August 5, 2004

so, for example, there is no "gateway address" (i don't know what the interface is, but if you're lucky once you hit the right option, the field "gateway address" or similar should be greyed out.

i'm not explaining this very well. this link explains the difference - you want to configure your router so it works like a hub (which will be possible - or you could just buy a cheapo hub!).
posted by andrew cooke at 6:03 PM on August 5, 2004

Response by poster: The second router that I'll use as a hub is a Linksys wrt54g. I found out how to turn dhcp off, but am having trouble figuring out where you can turn NAT off. still looking...
posted by Phatty Lumpkin at 6:11 PM on August 5, 2004

Response by poster: I'm guessing the NAT control in the linksys admin screen is where it says "firewall protection." I'll try disabling that.
posted by Phatty Lumpkin at 6:14 PM on August 5, 2004

Response by poster: I tried disabling dhcp and "firewall protection" in my linksys, and i couldn't get any ip addresses from the first router, which has DHCP turned on. The one computer that is directly plugged into the first router is receiving an ip address, but not those computers behind both routers.
posted by Phatty Lumpkin at 6:23 PM on August 5, 2004

it's not a firewall thing.

i just looked at my (belkin) wireless router. ignoring the fact that it's wireless - which is irrelevant here - i am using it as you want to use your router. i have dhcp and nat turned off. the nat on/off option is in "system settings" and labelled "warning experts only" (because normally, if it's a router, it needs to be on).

maybe someone with that particular router can help? otherwise, get a hub. they're real cheap (i have a dinky little one, the size of a cigarette card, cost maybe $15 dollars).

(bye - off to bed! :o)
posted by andrew cooke at 6:32 PM on August 5, 2004

cigarette box, not card! good luck.
posted by andrew cooke at 6:34 PM on August 5, 2004

Response by poster: Thanks for your help, Andrew. I'll keep looking for a way to turn NAT off.
posted by Phatty Lumpkin at 6:38 PM on August 5, 2004

How are you plugging the two together? Those cable/dsl WAP gateway things usually have an uplink port, probably labeled "Internet", and then they usually have 5 "LAN" ports, as well. So which ports does the ethernet cable connect?

The easiest thing to do would be to just get a cheap hub, like andrew said. Hell, if you feel like paying for shipping, I've got a 10Mbit 3com Superstack switch that I'm not using and would be happy to send you.
posted by cmonkey at 6:43 PM on August 5, 2004

After reading the users guide for your Linksys, it looks like you can only disable NAT for a single computer/IP address (page 72), which'll totally ruin your ability to use it to cascade connectivity. Best to just pop down to the local computer store and get a hub.
posted by cmonkey at 6:50 PM on August 5, 2004

cmonkey, that's just if you want one machine to bypass NAT. My Linksys router (which I don't have any more, or I could check the details more easily) had a choice between "gateway" mode and... non-gateway mode... in one of the areas of the configuration web page. Switching that mode should turn the router into a dumb hub pretty simply.
posted by bcwinters at 7:09 PM on August 5, 2004

My first thought was that you need a crossover cable between the two routers, as opposed to just a regular ethernet cable. You don't mention if you've done that, so excuse me if it's too obvious.
posted by crunchland at 7:22 PM on August 5, 2004

crunchland: switch to switch communication should work fine with a regular ethernet cable, they both should have autosensing built in to take care of that.

bcwinters: You're right, that would probably turn it into a dumb hub/access point.

But then again, most of my networking experience has been with corporate networks, so I might be assuming things about home network devices that simply aren't true
posted by cmonkey at 7:47 PM on August 5, 2004

Response by poster: My friend got his router recently, so we decided to exchange it for a switch and some change. Just have to hook it up now.
posted by Phatty Lumpkin at 7:48 PM on August 5, 2004

Response by poster: ...and it works. Thanks everyone!
posted by Phatty Lumpkin at 8:30 PM on August 5, 2004