Cabling question 568A

Hey Folks, quick question regarding cabling. I have two rooms, one is a telephony switch room and the other our main data center. I have two 568A patch panels in each room.

I have a 3750 switch (in the telephony room) trunked to the data center. My question is pretty straight forward. When does the cable usually cross over? I checked both patch panels wiring configuration and it seems to be straight through. Is it usually the case that you cross over the connection from the patch panel to the switch? Is panel to panel usually straight through?

Another question, even though the patch panel stated that it was 568A standard, the coloring scheme was (blue-white, blue, orange-white, orange, green-white, green, brown-white, brown) I found that odd considering 568A is (green-white, green, orange-white, blue, blue-white, orange, brown-white, brown) Why is that?

Thanks in advance,
Cameron

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Comments

hypnotoad

The 3750 will use "auto-mdix" on the interfaces so it will use either a crossover or a straight-through...

Auto-MDIX - Wikipedia, the free encyclopedia

Netwurk

I've seen a lot of cabling in my day and I've learned to make sure that the blue wire on the one end matches the blue wire on the other end, and that blue-white on one end matches blue-white on the other end, etc.

In other words, if the color scheme doesn't match 568A or 568B, just make sure wires 1 thru 8 are the same colors on both ends (assuming you want straight-through cabling). Patch panel testing gear is also very helpful, but I understand that it is not always readily available. Of course neither are old pros like me. Remember kids, America works best when we say Union Yes (old pro ignores the silly booing of the neocons).

Of course 3750s also need to be cabled together with the stackwise cables (special thanks to the former intern I trained years ago for letting me "help" with the new switches at work or I would have no idea what a stackwise cable is).

So I hope the above helped.

God bless America, we sure need it.

tiersten

Netwurk wrote: »

I've seen a lot of cabling in my day and I've learned to make sure that the blue wire on the one end matches the blue wire on the other end, and that blue-white on one end matches blue-white on the other end, etc.

In other words, if the color scheme doesn't match 568A or 568B, just make sure wires 1 thru 8 are the same colors on both ends (assuming you want straight-through cabling).

Don't mess up the pairing tho. Arbitrary assignment of the different wires will probably end up with the pairs not twisted together any more.

Auto-MDIX will only work if you've got autoneg enabled. If you've forced it to anything then auto-MDIX will fail.

tech-airman

clamz,

clamz wrote: »

Hey Folks, quick question regarding cabling. I have two rooms, one is a telephony switch room and the other our main data center. I have two 568A patch panels in each room.

I have a 3750 switch (in the telephony room) trunked to the data center. My question is pretty straight forward. When does the cable usually cross over? I checked both patch panels wiring configuration and it seems to be straight through. Is it usually the case that you cross over the connection from the patch panel to the switch? Is panel to panel usually straight through?

Before I answer your question I have a question. When you mention "...trunked to the data center..." what networking device is located in the data center that this "3750 switch" is connected to?

clamz wrote: »

Another question, even though the patch panel stated that it was 568A standard, the coloring scheme was (blue-white, blue, orange-white, orange, green-white, green, brown-white, brown) I found that odd considering 568A is (green-white, green, orange-white, blue, blue-white, orange, brown-white, brown) Why is that?

Thanks in advance,
Cameron

If the wire coloring scheme that is being used is "...(blue-white, blue, orange-white, orange, green-white, green, brown-white, brown)..." then the patch panel is lying. In order to be proper 586A standard, the wire coloring scheme should be (white-green, green, white-orange, blue, white-blue, orange, white-brown, brown). Notify your supervisor that the patch panel is in violation of 568A.

clamz

tech-airman wrote: »

clamz,

Before I answer your question I have a question. When you mention "...trunked to the data center..." what networking device is located in the data center that this "3750 switch" is connected to?

It is trunked to two 4500 catalyst switches.

tech-airman wrote: »

If the wire coloring scheme that is being used is "...(blue-white, blue, orange-white, orange, green-white, green, brown-white, brown)..." then the patch panel is lying. In order to be proper 586A standard, the wire coloring scheme should be (white-green, green, white-orange, blue, white-blue, orange, white-brown, brown). Notify your supervisor that the patch panel is in violation of 568A.

You know what, I did some researcha nd it is infact 586B, not 568A. I guess on the patch panels the pin outs count like this, 5 - 4 - 1 - 2 - 3 - 6 - 7 - 8

So given that rationale, it is (blue-white, blue, orange-white, orange, green-white, green, brown-white, brown)

Hypno, I do believe these switches have auto-mdix configured, thanks for that knowledge.

-clamz

dynamik

How to Make a Category 5 /5e Patch Cable

tech-airman

clamz,

clamz wrote: »

It is trunked to two 4500 catalyst switches.

So let's take one channel between the 3750 switch and one of the 4500 catalyst.

[4500 Catalyst Switch]---(crossover)---[Patch Panel]-(straight-through)---[Patch Panel]--(straight-through)--[3750 switch]

or

[4500 Catalyst Switch]---(straight-through)---[Patch Panel]---(straight-through)---[Patch Panel]---(crossover)---[3750 switch]

clamz wrote: »

You know what, I did some researcha nd it is infact 586B, not 568A. I guess on the patch panels the pin outs count like this, 5 - 4 - 1 - 2 - 3 - 6 - 7 - 8

So given that rationale, it is (blue-white, blue, orange-white, orange, green-white, green, brown-white, brown)

You mentioned "586B", are you sure? Don't you meant 568B.2? You mentioned "...(blue-white, blue, orange-white, orange, green-white, green, brown-white, brown)..." which is NOT the 568B.2 standard so it's a violation of 568B.2. 568B.2 requires (white-orange, orange, white-green, blue, white-blue, green, white-brown, brown). When you mention "...pin outs..." what are you talking about?

clamz wrote: »

Hypno, I do believe these switches have auto-mdix configured, thanks for that knowledge.

-clamz

hypnotoad

tiersten wrote: »

Don't mess up the pairing tho. Arbitrary assignment of the different wires will probably end up with the pairs not twisted together any more.

Auto-MDIX will only work if you've got autoneg enabled. If you've forced it to anything then auto-MDIX will fail.

2 good points there. I'm not a big fan of wiring or (standards for that matter)!

clamz

tech-airman wrote: »

clamz,

So let's take one channel between the 3750 switch and one of the 4500 catalyst.

[4500 Catalyst Switch]---(crossover)---[Patch Panel]-(straight-through)---[Patch Panel]--(straight-through)--[3750 switch]

or

[4500 Catalyst Switch]---(straight-through)---[Patch Panel]---(straight-through)---[Patch Panel]---(crossover)---[3750 switch]

Hey, I originally thought that the first example that you made was the way it connected. After reading hypno's post, I did a

do sh controll eth fa0/32 phy | i MD

I found out that auto-mdix is enabled on the 3750 interface. So therefore, I determined that all cables are straight through and the 3750 crosses over the connection via auto-mdix on that interface.

You mentioned "586B", are you sure? Don't you meant 568B.2? You mentioned "...(blue-white, blue, orange-white, orange, green-white, green, brown-white, brown)..." which is NOT the 568B.2 standard so it's a violation of 568B.2. 568B.2 requires (white-orange, orange, white-green, blue, white-blue, green, white-brown, brown). When you mention "...pin outs..." what are you talking about?

I think a image would better suffice to explain my logic,

Netwurk

tiersten wrote: »

Don't mess up the pairing tho. Arbitrary assignment of the different wires will probably end up with the pairs not twisted together any more.

Agreed - the workaround of "color-matching" is for wiring that doesn't follow the standard pairings. I'm definitely not for arbitrary wiring. Some wiring is so bad that you can't even see the colors and in that case you should try a different wire brand/vendor if that's something you can influence.

When the wiring is run to a patch panel, you really really need good wires that follows the code - otherwise a lineman trying to help you won't be able to (or your boss will pay a lot to have him run wire traces and/or replace wiring).

The MDIX workarounds are OK, but only work if the cable is truly a crossover. If the wiring is totally FUBAR, then you've got to redo it.

tech-airman

clamz,

Now that I've got enough information, I'll directly answer your questions:

clamz wrote: »

Hey Folks, quick question regarding cabling. I have two rooms, one is a telephony switch room and the other our main data center. I have two 568A patch panels in each room.

I have a 3750 switch (in the telephony room) trunked to the data center. My question is pretty straight forward. When does the cable usually cross over?

The trunk channel is usually crossed over by the use of a crossover patch cable in either the "telephony room" or the data center BUT NOT BOTH. If you use crossover patch cables in both the "telephony room" and data center, the first patch cable crosses over then the second patch cable un-crosses the channel effectively making it a straight through.

clamz wrote: »

I checked both patch
panels wiring configuration and it seems to be straight through. Is it usually the case that you cross over the connection from the patch panel to the switch?

Yes, by the use of a single crossover patch cable from the switchport to the patch panel.

clamz wrote: »

Is panel to panel usually straight through?

Yes, the channel between patch panel to patch panel should be straight-through.

clamz wrote: »

Another question, even though the patch panel stated that it was 568A standard, the coloring scheme was (blue-white, blue, orange-white, orange, green-white, green, brown-white, brown) I found that odd considering 568A is (green-white, green, orange-white, blue, blue-white, orange, brown-white, brown) Why is that?

Since a picture says a million words, the punch down block part of the patch panel does NOT directly correspond with the pin numbers inside the 8 position modular jack. You control the type of channel the patch panel to patch panel link by using the various punch down order. I think that the manufacturer of that patch panel "legend plate" just wanted to be lazy by keeping the blue and brown pairs that don't change on the ends then just swap the middle pairs in the printing process at the cost of warping the numerical order of the pins and confusing people like me.

clamz wrote: »

Thanks in advance,
Cameron

Do you have any further questions? Did my posts help?

clamz

Hey Tech, yeah thanks for all the info. I can say I took away a lot of valuable knowledge from this post. Thanks everybody

NetAdmin2436

I would encourage anyone who works with wiring to get a cable/data tester. This little device can save you lots of headache when dealing with random connectivity issues. This one below was about $80 at Home Depot that does coax and has a few bells and whistles.
IDEAL INDUSTRIES, INC. - VDV MultiMedia Cable Tester Kit

There are cheaper testers that would work too, depending on your needs.

tiersten

NetAdmin2436 wrote: »

I would encourage anyone who works with wiring to get a cable/data tester. This little device can save you lots of headache when dealing with random connectivity issues. This one below was about $80 at Home Depot that does coax and has a few bells and whistles.
IDEAL INDUSTRIES, INC. - VDV MultiMedia Cable Tester Kit

There are cheaper testers that would work too, depending on your needs.

Cheaper testers tend to only do continuity tests though.