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RE: E1 - RJ45 pinout with ethernet crossover cable

  • From: Hannigan, Martin
  • Date: Fri Feb 25 09:50:26 2005


> -----Original Message-----
> From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of
> Sam Stickland
> Sent: Friday, February 25, 2005 6:26 AM
> To: nanog@nanog.org
> Subject: E1 - RJ45 pinout with ethernet crossover cable
> 
> 
> 
> Hi,
> 
> Quick question: If I have two E1 ports (RJ45), then will running a 
> straight ethernet cable between the two ports have the same affect as 
> plugging a ballan into each port and using a pair of coax (over a v. 
> short distance).

If I understand you correctly, you can eliminate the coax
altogether with a standard t1/e1 cable betweem the dsu's:

  1        2      3     4       5       6    7    8  

RX Tip  RX Ring  n/c  TX Tip  TX Ring  n/c  n/c  n/c  

Just for reference, here's ether xover:

Crossover Cable  (EIA/TIA 568A)

RJ-45  PIN RJ-45 PIN 
1 Rx+  3 Tx+  
2 Rc-  6 Tx- 
3 Tx+  1 Rc+ 
6 Tx-  2 Rc- 


> Likewise would using an ethernet crossover cable have the 
> same affect as 
> swapping the pairs round on one balland.

Not that I know of, but I've never attempted what you 
describe. Putting the baluns in the loop will destroy the
framing i.e. it's going to try and convert b8zs/ami to 802.x.

[ SNIP ]

-M<