rj45 types/pinouts etc??

[Cramig88]

ok so whats with all the different pinouts as related to rj45/ethernet cables?  pardon my misunderstanding but it seems pretty silly to me...

for example types A and B are the same except the orange and green pair.  i mean in a network u could mix cables, so long as either side match.  that being said, why is there an A type and a B type?  taking a guess... but the pairs being twisted reduces crosstalk - one reason why solid isnt on one half and striped being on the other?

aside from that uh MDX or something eliminates the need for a crossover cable with modern equipment circa idk 2010?  blah moving on to my main question

why are there 2 different types of crossover cables?  one is 568A to 568B then another is completely wacky shoving the blue pair to 7/8

i forget what its called but it goes like this, regardless of 568A or B, your at 1-8

so:

1 2 3 4 5 6 7 8 on one side

3 6 1 8 7 2 5 4 on another

 

as mentioned A to B just changes 2 pair, so.... whats ^that all about?  not that its needed anymore with equipment these days, just curious

 

thanks peeps!

[ieleja]

Not all hardware in use can deal with this MDI-X thing and safer/better is use A or B in one building...

[mariushm]

There's T568A (starts with green) and T568B  (starts with orange) 

 

With 100 mbps ethernet cards, if you want to create a direct connection between two computers, you need a crossover cable, where the TX pair from one PC goes into the RX input of the other PC. Hence why the two pairs of wires are switched in one connector. 

 

I'm not 100% sure but I think the reason why the B version is preferred in cables made automatically (patch cables etc) is because the way the pairs are twisted, it's easier for automated machines to untwist pairs, and rearrange the wires. 

 

 

With 1 gbps or higher ethernet cards, all four pairs are used to transmit data, so all four pairs would have to be twisted, but 1 gbps and higher ethernet cards are supposed to have automatic pair detection making crossover cables no longer needed. 

 

but if you want to actually make a crossover gigabit cable it would look like this, either one of the two versions would work.

 

[Cramig88]

1 hour ago, mariushm said:

There's T568A (starts with green) and T568B  (starts with orange) 

 

With 100 mbps ethernet cards, if you want to create a direct connection between two computers, you need a crossover cable, where the TX pair from one PC goes into the RX input of the other PC. Hence why the two pairs of wires are switched in one connector. 

 

I'm not 100% sure but I think the reason why the B version is preferred in cables made automatically (patch cables etc) is because the way the pairs are twisted, it's easier for automated machines to untwist pairs, and rearrange the wires. 

 

 

With 1 gbps or higher ethernet cards, all four pairs are used to transmit data, so all four pairs would have to be twisted, but 1 gbps and higher ethernet cards are supposed to have automatic pair detection making crossover cables no longer needed. 

 

but if you want to actually make a crossover gigabit cable it would look like this, either one of the two versions would work.

 

Does this make any difference with PoE?  For example my net gear switch supports it on 12 of 24 ports - I’d like to use one as a AP without the need for power, as opposed to an outlet of course 

[mariushm]

Makes no difference, just have the same order on both ends. Best to use a regular patch cable you buy from the store with connectors preinstalled.

 

It may be worth making your own cable if you need a lot of power through the cable (as in more than let's say 50 watts), you'd use proper solid core AWG23 cables and the right ethernet connectors.