Double Routing

Like prob­ably every oth­er com­puter geek out there, I do a cer­tain amount of help­ing friends set up their home sys­tems. This par­tic­u­lar friend knows noth­ing about net­works and fire­walls and the like, and just wanted some­thing secure that would allow her to have a reas­on­ably safe Win­dows box and the daugh­ter to have a reas­on­ably safe and vir­us-free Win­dows laptop. The easy bits were installing the spy­ware detect­ors (Ad-Aware and Spy­bot S&D) and the vir­us checker/utilities (Norton Sys­tem­Works); the tough bit was get­ting the routers to work.

The sys­tem that made most sense was to feed the DSL into a wired eth­er­net router with a built-in fire­wall (the D‑Link DI-604 has a reas­on­able price point and an integ­rated fire­wall) and then set up a wire­less point for the daugh­ter­’s laptop. So my friend got a Link­sys wire­less router (no fire­wall). We have this sys­tem at home, though with dif­fer­ent hard­ware (Linux fire­wall + Air­port wire­less) and it works just fine. So I was­n’t expect­ing any oddit­ies. I found the sup­port page on the Link­sys site that said to turn off the DHCP serv­er on the wire­less router, and to give it an IP address that fit­ted in with the IP setup of the wired router. That was easy enough to do. But some­how the laptop just nev­er man­aged to sync up.

Ah, how good it was that I allowed more time than I expec­ted to need to set it up! My basic idea was that eth­er­net comes out of the DSL mode, goes into the wired router in the uplink sock­et, then a cable comes out of the wired router and goes into the uplink sock­et of the wire­less router. Still seems logic­al to me, but in this case my logic was com­pletely wrong. For­tu­nately Link­sys has live chat to tech sup­port that works on a Sat­urday (good move, people!) and Mel­rose did­n’t need very long to fig­ure out the prob­lem and tell me to put the cable com­ing out of the wired router into one of the 4 reg­u­lar sock­ets. This worked just fine; the laptop synced up, my friend (and her daugh­ter) are happy and think I know exactly what I’m doing, while I’m still slightly baffled and won­der­ing what’s wrong with my simple hose-pipe ana­logy of inter­net con­nec­tions. Still, I now know empir­ic­ally what to do, so that’s the import­ant thing.