Really Weird Wiring Problem

[amorielljr]

I'm having a really strange problem with my Cisco 6509 and our telco patch cabling. Currently in our datacenter we installed patch pannels in our switch racks to connect those switches to servers or other switches in other racks. The cable for these patch pannel is telco style (basically it's one fat cable with a special DB connectors at each end which hooks on each side to a 48-port patch pannel). We hooked up one of our Cisco 6509s and when we try to connect it to another switch (a Cisco 2950) , we can't get any physical connectivity. Over the same cabling we can connect other Cisco switches together. The only difference that I noticed between this cable and regular cat5e is that it only uses the pairs that are needed and the pairs that are not used do not exist (our cable tester shows them as open). Does anyone have a suggestion?

 

[RookThis]

Have you tried the following? Moving the 2950 to one of the connections where another switch is working. That will tell you if it's the cable or not.

 

[amorielljr]

It's definetly the cable, you can connect the two switches together by using a regular crossover cable. I was wondering if the 6500 (with sup 720) checks to make sure that all pairs on the cat5 cable are working.

 

[RookThis]

Did you check to see if the switch would work if you moved it to a connection where another switch is working? If it works there, then the physical pairs in the telco cable are probably bad.

 

[kcbell]

May be a long shoot! Look into 568A and 568B on cable and termination. Our whole company is 568B except one cabinet. You cannout believe how much time we were wasted.

 

[amorielljr]

The 6509 will on work on any of my telco cabling. However other Cisco switches and hosts work. The only explanation that I can conceive is because the telco cable connects only the wires used (pins 1, 2, 3, and 6) and the other wires are left open (they don't exist). I'm guessing that maybe the 6509 tests all pairs and it some are left open; it views the cable as bad or nonexistent. Any thoughts??

 

[RookThis]

Well you can prove that by making a cable with only the pins that are used and see if that works that will prove if the switch requires it or not. What type of line card are you using you never specified that. What is the part number of the cable? Do you have the schematic on how it's terminated, 568A or 568B?

 

[baddos]

Does the interface show as "Down" and "Down"?

The switch will only use 1,2,3 and 6 so it shouldn't matter if the other wires aren't connected.

Do like RookThis says and make a custom cat5 cross-over cable and see if that works.

 

[amorielljr]

Yes, it does show down, down (not connected). I will make a cable to test this. I'll let you know the results.