Problem connecting a router to a switch
Posted on 2006-06-07
I'm having the following issue regarding the connection of a router to a switch:
I have a Linksys wrt54gc broadband router, it has wireless functionality, but that doesn't has anything to do with the problem. Also, I have a 3net 8-port switch (ALN-5008T) which is supposed to be 'intelligent'.
I ha ve a friend in the next floor who has a DSL connection to the Internet; the ISP assigns a maximum of 4 IP addresses dinamically via DHCP. So we decided to share his connection, connecting my 3net switch directly to the DSL modem. When we connect our 2 main PCs to the switch using straight-thru ethernet cables, we get 2 different IPs from our ISP; so far, it works fine. So I thrown an ethernet cable from his department thru mine, leaving the switch in his department. It still worked fine.
But then I decided to place the router mentioned above in my department, in order to share the connection between my two PCs, and there started the problem; I connected the same straight-thru cable I had in the PC to the 'Internet' port of the linksys, and connected the PC (straight-thru also) to a regular port of the router. The linksys router connected to the ISP, got an IP address and connected to the DNS servers.
I can ping from my PC and from inside the router. I can receive and send email using mail clients (which indicates that at least some ports and services are working in some level), but I can't browse the internet.
I´ve already tried changing the cable that goes from the switch to the Internet port of the router, from straight-thru to crossover, and it didn't work anyway. I discarded a problem of communication between the router and the switch inverting their position (connecting the router to the switch, and then the PCs to the Switch; it worked perfectly). Both the switch and the router work using IEEE 802.3 and 802.3u. I made (I think) every possible combination of cables (crossover or straight-thru) between PCs, router, modem and switch; but when the router is subordinated to the switch, there is no way to make it work.
Finally, a friend borrowed me a Hub. I made the desired connection using the right cables, and I got to make it work connecting the Hub to the Modem, the a PC and the Router to the Hub, and the other 2 PCs to the Router. Everything worked fine. But I need this to work without the borrowed hub, and using my own switch.
There must be something I don't know about, or maybe something really stupid i'm totally missing. I have two days searching the net for answers, but nobody seems to have tried to connect a router and a switch in that particular way (everybody connects the router to the modem, and the switch to the router; I need router and modem inverted).
I hope somebody has an answer on this... if not, this is probably going to be sadistically fun, as it has already been for me...