RJ45 problems 2

[OldSkoolSkater]

I came across a problem today where the PCs at work would not ping ip addresses on the network (network connectivity was really bad for all apps and browsing). Managed to track it down to a network point that had cores 2 & 7 open circuit, punched them back in and the network was fine.
My question is why an o/c on core 2 would cause such a major problem. Any ideas?

Cheers

Steve - Network Coordinating in the UK

 

[bierhunter]

Avaya, I think the confusion with your post is that it seems to be assuming full-duplex, because it's a switch. With full-duplex, you shouldn't have collisions. You can still have half-duplex connections on a switch in which case you can still have collisions on that segment. Switches don't eliminate collisions just for being switches. Everything still has to be configured and working properly too.

 

[AvayaNovice]

Correct. I should have stated I'm assuming 100MBit full duplex, as that is what most switches/NICs default to in their autonegotiation.

 

[wires]

Switches have their place but they are not the "cure all" that current marketing literature makes them out to be.

YES - switched networks have collisions. Take the example of a small network with one server that also serves as a gateway. The switch port with the server/GW is in essence a "shared" segment with all of the client PC's. Unless there is peer-to-peer network traffic a single server/GW network will see NO improvement when changing from a hub to a switch.

On a managed hub (where you can see such things) you will see several statistics for collisions. Nortel switches commonly report Collisions, Single Collisions, Multiple Collisions, Excessive Collisions and Late Collisions as discrete values for each port.

It does not matter how many lanes a superhighway has if everybody is going to the same BBQ joint, there will be a traffic jam...

In my opinion there are WAY too many switches being installed. Switches (especially cheap ones) have their own set of problems and add complexity to a network. I have never had to "reboot" a hub but I have seen networks malfunction when a switch's tables get horked and need to be reset. Spambots and other network "evildoers" are much easier to find on a hub network than a switched one.

Appropriate use of technology should be the design goal. Ethernet is a shared media and collisions are a part of that design. Unless collisions reach unacceptable levels there is no need to worry about it or install switches.

That is my usual "switch" rant. As to the original question my guess is either what Servamatic said or noise on pin 1 (unbalanced due to pin 2 open) causing problems on the switch.

 

[Servamatic]

Wires....

I could not have said it any better than that...enjoyed the superhighway and BBQ joint analogy.

Richard S. Anderson, RCDD

http://www.servamatic.net

 

[wires]

Whoops!

"On a managed hub (where you can see such things) you will see several statistics for collisions."

Should have been:

"On a managed SWITCH (where you can see such things) you will see several statistics for collisions."

Sorry!