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). Likewise would using an ethernet crossover cable have the same affect as swapping the pairs round on one balland. Or are the pinouts different to ethernet? I tried googling but couldn't find anything (perhaps because I can't seem to spell ballan :/ ). Sam
On Feb 25, 11:25am, Sam Stickland <sam_ml@spacething.org> wrote:
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).
You generally need a router or something else acting as store-and-forward. E1/T1 and other plesiochronous circuits are just that, near synchronous, and certainly not asynchronous. Things cannot be transmitted or received without clocks on both sides being in synch, which may or may not be the case if you try to hook up two arbitrary lines. Moreover, assuming both are terminated towards you, both will be driving clock for your router ("terminal equipment") to pick up, and they are not going to be in phase. Then there's the issue of different options for framing and various control bits, etc. You might get lucky if you could convince one of the circuit providers to take clock from you (which would then come from the other circuit), but you would probably still need to deal with signal level, framing, and other issues (ie, have a box of sorts). All in all, an old cisco 2500 is probably the cheapest and most troublefree solution.
Or are the pinouts different to ethernet? I tried googling but couldn't find anything (perhaps because I can't seem to spell ballan :/ ).
It's balun -- BALance-UNbalance. Best, -- Per
--On 25 February 2005 11:57 +0000 Per Gregers Bilse <bilse@networksignature.com> wrote:
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).
You generally need a router or something else acting as store-and-forward. E1/T1 and other plesiochronous circuits are just that, near synchronous, and certainly not asynchronous.
Whilst this is true, his question still stands. Yes indeed if you got the RJ-45 crossover right (I don't think it's ethernet pinout from memory, but...) you would indeed achieve the same effect as a crossed over pair of coaxes. However, it might well not be the effect you intend or desire (for the reasons Per points out). One circumstance where this does work is connecting (for instance) an E1 trunk connection between (say) two FR switches in the same room, provided you remember to set exactly one end to originate, and one end to receive clock (i.e. where there are no carriers involved). Alex
On Feb 25, 12:03pm, Alex Bligh <alex@alex.org.uk> wrote:
One circumstance where this does work is connecting (for instance) an E1 trunk connection between (say) two FR switches in the same room, provided you remember to set exactly one end to originate, and one end to receive clock (i.e. where there are no carriers involved).
Fair enough. Pin-out is not the same as ethernet, but same idea; there's a very clear diagram here about 2/3s down the page: http://www.nettonet.com/support/docs/220-0000081_r01.n2n -- Per
On Fri, 25 Feb 2005, Per Gregers Bilse wrote:
You generally need a router or something else acting as store-and-forward. E1/T1 and other plesiochronous circuits are just that, near synchronous, and certainly not asynchronous. Things cannot be transmitted or received without clocks on both sides being in synch, which may or may not be the case if you try to hook up two arbitrary lines. Moreover, assuming both are terminated towards you, both will be driving clock for your router ("terminal equipment") to pick up, and they are not going to be in phase. Then there's the issue of different options for framing and various control bits, etc. You might get lucky if you could convince one of the circuit providers to take clock from you (which would then come from the other circuit), but you would probably still need to deal with signal level, framing, and other issues (ie, have a box of sorts). All in all, an old cisco 2500 is probably the cheapest and most troublefree solution.
In every case I've dealt with when setting up a back-to-back connection of T1 or E1 circuits, the appropriate crossover connection between transmit and receive (1,2 - 4,5 on 8-pin jacks, swap Tx and Rx on co-ax) and setting one side to supply internal clock and the other side to recover clock from line works just fine. -- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net WestNet: Connecting you to the planet. 805 884-6323 WB6RDV NetLojix Communications, Inc. - http://www.netlojix.com/
On Fri, 25 Feb 2005, Sam Stickland wrote:
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).
Not straight, you need to make or buy a special crossover cable unless you're going from a CSU to a terminal equipment port, in which case a straight cable will work if it has all four pairs connected. Some cheap cables sold for ethernet use only have pairs 1,2 and 3,6 wired. These will not work as T1/E1 uses 1,2 and 4,5.
Likewise would using an ethernet crossover cable have the same affect as swapping the pairs round on one balland.
I think you mean "balun". A crossover cable for T1/E1 is pairs 1,2 and 4,5 swapped which is blue/white and green/white for 568A.
Or are the pinouts different to ethernet? I tried googling but couldn't find anything (perhaps because I can't seem to spell ballan :/ ).
Well, the modular jack connections are balanced and coaxial cable is unbalanced. You don't need baluns unless you're going from BALanced on one end to UNbalanced on the other (hence the name balun). Get a straight-through cable. and look at it. If the insulation on the left two pins is green when holding the contacts up and away from you, then cut off one end and reassemble it with the green and blue pairs swapped around. If orange, then swap the orange and blue. If brown, turn it over and look again. :-) Set ONE of your devices to provide clock ("Internal") and the other to recover clock from the line ("Network"). If either of the devices is also connected to a carrier or other network by T1/E1, clocking can get more complicated and you probably want to consult a local expert on that particular equipment. -- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net WestNet: Connecting you to the planet. 805 884-6323 WB6RDV NetLojix Communications, Inc. - http://www.netlojix.com/
participants (4)
-
Alex Bligh -
Jay Hennigan -
Per Gregers Bilse -
Sam Stickland