How to connect dsl router through ethernet LAN switch

[MauriceIRL]

I have a ZyXEL P-660HW-T1 v3 modem router, and a Linksys SD216 16-Port 10/100 Desktop Switch. I have two Macs and several ethernet cable connected devices, e.g. printers etc. Until the DSL side of my telephone and ISP phone line developed a fault some days ago, everything worked perfectly, i.e. I had internet and email on both Macs, and all the networked devices were accessible. The DSL line fault appears to have been fixed, but I can only get internet and email on one Mac when this is connected directly to the modem router.

Not suspecting that the DSL side of the phone line was faulty, as the telephone side was working perfectly, I thought that the modem router was faulty, and purchased a NETGEAR N300 DGN2200v4 modem router, but with the same result e.g. I can only get internet and email when one Mac is connected directly to the modem router.

I have tried connecting both modem routers (separately, not together) through the ethernet switch, as I remember it before the DSL fault appeared, i.e. with normal ethernet cables from Mac to switch and from switch to modem router.

What might I be doing wrong, please?

MauriceIRL

 

[Tradesman1]

My guess is if the new router is out of the box, it may well be trying to use the same IP as your DSL modem router, why not just connect all direct to the switch - 16 ports is more than enough, or eliminate the switch altogether

 

[MauriceIRL]

Thanks, Tradesman1.
Actually, I found the cause of the of the problem and fixed it.
I forgot to mention in my original posting that I had removed my ZyXEL modem router temporarily to help someone who needed to check his very old modem router. Believe it or not, when I reconnected the this modem to my own computer and switch, I accidentally connected one Ethernet cable to two ports on the switch—duh! Removing this cable altogether fixed the problem, naturally . . .

 

[Tradesman1]

That could cause just a bit of a problem