mnemonic.
Today I had to wire up some Category 5e ethernet cabling. I’ve had to do this since I started working in IT but every time I’ve had to resort to looking up the TIA/EIA586B spec via Wikipedia to get the wiring correct.
I’m kind of sick of this, so I came up with a mnemonic to remember it. I’ve seen one but it involved boobies so it’s not really suitable for a work environment. Well, most, anyway.
You have to remember 2 things though:
1. Each pair consists of a Colour/White strand and a White/Colour strand. The Colour/White strands (pins 2,4,6,8) are in UPPERCASE, and the White/Colour strands (1,3,5,7) are in lowercase.
2. Both Blue and Brown start with the letter B, so for Brown I use the letter ‘R/r’, being the second letter. Blue has no letter R so this avoids ambiguity.
If we take o=Orange, g=Green, b=Blue, r=bRown, this gives us:
o O g B g G r R
1 2 3 4 5 6 7 8
If we split this into even/odd pins, we get
o g b r for the odd pins
O B G R for the even pins
The mnemonic is:
our good boys run Over Bloody Great Rails
So next time you have to hand crimp some Cat5e just say this to yourself, and remember the first 4 are the odd pins and the last 4 are the even ones.
Bear in mind this is only valid for TIA/EIA586B. For non-PoE A/B crossover cable, just swap the Green and Orange pairs round at one end. I haven’t thought of a mnemonic for this one yet, though, so you’re on your own. A word of warning though! This will only work for data-only Cat5e — you risk seriously damaging your kit if you run Power over Ethernet or phone signals through this kind of crossover cable. Something tells me that your average onboard Ethernet chipset will not appreciate having 48V DC shoved up its backside.
Remember, with the advent of widespread support for Auto-MDIX there is often no need to run x-over cabling at all and just using straight B-B cabling is the best idea unless neither of the PHYs on either end support auto-MDIX.
For the rj-45 chart:
Orange White
Orange
Green White
Blue
Blue White
Green
Brown White
Brown
=
One Woman,
One
Good Woman -
Beats
Bad Women
Getting
By With
Brutality
I known the B’s can get confusing, so note the R in BRutality, tipping the BROWN to you.
once Osama got Blighty bloodied George brought BROUHAHA!
The beauty of this mnemonic is that solid colours are denoted by proper nouns so all have upper case letters, and the blues and browns are differentiated with the second letter of the colour being correct in each case. Of course the exception is BROUHAHA, which is not a proper noun and therefore should actually be a lower case letter, but remeber that word in upper case and it kinda fits. The other downsides are that nobody seems to know that Blighty is slang for Britain, and of course the whole story is completely untrue, but hey, it’s a mnemonic, not a history lesson.