Re: two pairs cross utp cable for auto-mdix

From: Mark Lasarko (mlasarko@co.ba.md.us)
Date: Mon May 15 2006 - 12:21:45 ART


I cannot confirm on that blade, WS-6748-GE-TX.
However I have unlinked a GigE connection from a 3550 to various devices using
a "standard" crossover (only pins 1,2,3,&6 crossed).

Depending on what type of device I plugged into...

A WS-X4448-GB-RJ45 negotiated some flow control
(input flow-control is off, output flow-control is on )

Whereas an inexpensive Linksys(Cisco) switch did not negotiate any flow
control.
(input flow-control is off, output flow-control is off)

In both cases, switch to switch, the "standard" X-over worked to some extent.
Yet even though it "linked-up", performance may still be a factor if FC is not
proper.

I was recently told by a friend who is an RCDD to use a "fully crossed" cable
when up linking Gigabit Ethernet.

Here's an example of a fully crossed TIA/EIA568B cable
1 (Or/W) > 3
2 (Or) > 6
3 (Gr/W) > 1
4 (Bl) > 7
5 (Bl/W) > 8
6 (Gr) > 2
7 (Br/W) > 4
8 (Br) > 5

As you can see the other two pairs are also crossed.
I have read various opinions on this...
I would see what the 'sh int' offers once you connect.

w/ PoE that's another can of worms... diodes get in the way and don't seem to
care about the other pairs,
but we are talking switch-to-switch here, so hopefully this is helpful to
you.

Cheers,
~M

>>> Tom Young <gitsyoung@yahoo.co.jp> 05/15/06 8:36 AM >>>

CCO said it is could use any type cable to connect the
switch that has auto-mdix function.
May I connect WS-6748-GE-TX to Cat3550's Giga interface
with a two pairs twisted CROSS-OVER
cable that 4,5,7,8 pin has a straight pinout? The cable is
Cat5e.Does that could support 1000BASE-T ?

thanks alot

--------------------------------------
Yahoo! JAPAN 10th Anniversary Special Feature
--- Enjoy Yahoo! Auction with Yahoo! Mail !! ---
http://pr.mail.yahoo.co.jp/auction/



This archive was generated by hypermail 2.1.4 : Thu Jun 01 2006 - 06:33:21 ART