I figured out an intermittent adsl problem | when using a switch

[dagwood4455]

a network guy installed a 8-hub switch upstairs in my house yesterday. Attached to this hub was a TV, Bluray player, a mac and a Dlink WAP (wireless access point). I have always had two network cables that go upstairs (modem is downstairs).

This is whole set-up quite a risky thing to have as I have very little knowledge about networks nor multimedia stuff (i just watch them).

Anyway soon after the network guy left I 'just checked he cables' and made tidy. I found a loose network cable, stuck it into the switch/hub and started "enjoying" this new smart tv experience. Then the tv started going on an off, the internet connection of the whole house became intermittent and slow at times.

Eventually I found out that i should not have stuck that loose cable into the switch; you see it was the second cable from the modem / router to upstairs. Now i had two cables of the modem attached to the switch, which caused the problem.
Lesson learned: one should never have two / duplicate cables from a router to a switch/hub.

 

[Know_hope]

Correct!

You essentially created a Loop in your network, causing a broadcast storm between the router and the switch! Doh!!!!

 

[Tinuva]

Alternatively, i you have equipment that support port-channels, you should do that, which means redundancy and possible having the speed from both cables. Sadly I doubt many, if any, adsl modem/routers support that.

 

[thisgeek]

Alternatively, i you have equipment that support port-channels, you should do that, which means redundancy and possible having the speed from both cables. Sadly I doubt many, if any, adsl modem/routers support that.

Your basic SoHo consumer equipment won't.

 

[TheGuy]

Alternatively, i you have equipment that support port-channels, you should do that, which means redundancy and possible having the speed from both cables. Sadly I doubt many, if any, adsl modem/routers support that.

It's spanning tree that does this right?

 

[yaeger]

It's spanning tree that does this right?

Yep.

 

[PsyWulf]

Collide and loopback ftw

Simple explanation is any broadcast message from any device on the network is repeated by the hubs,if the hub receives a message it sends it again,causing the little memory they have to fill up with junk crippling the entire network

Once has one of my previous job's Call Centre branches fall over every few minutes. After much diagnosing and shutting down network segments I find a Network point plugged into a hub which already had an uplink to the serverroom. So any time that segment started up that section would get network issues and it would spread through the entire network from there

 

[Pada]

We've had this issue with Neotel a few months back, when one of their network guys did an unscheduled loopback test 10'o clock the evening on a weekend, and then our Cisco router simply switched off our fiber connection completely and it didn't come back online after the guy removed the loopback.
So ja, we've had quite a bit of a discussion with Neotel regarding that test that they did, because our systems was offline for more than 12 hours due to that little experiment.