GigaStack GBIC

[shovels3]

We have Cisco 2950's daisy chained.

we need to add another 2950 to the stack

But require a cable longer than the CAB-GS-1M

will i have to use fibre?

This is what cisco say...

You must use one of the Cisco proprietary cables (CAB-GS-50CM or CAB-GS-1M). If you use any other cable, you will not have connectivity.

[konigl]

You can use SX GBICs and multimode fiber, but it is not absolutely necessary.

If you are out of range with respect to the GigaStack cable length, you could use the 1000BASE-T GBICs and a Gigabit Ethernet cross-over cable. That would give you a distance of 100m to play with. These GBICs are less expensive than the fiber ones, but more expensive than the GigaStack ones.

The Gigabit cross-over cable is similar to a 10/100 cross-over cable, but with all four pairs crossed. Both use Category 5 or better UTP cable.

On a 10/100 cross-over, the critical pinouts are as follows:

5------3

4------6

3------5

6------4

the rest can be straight-through (that is, 1----1, 2----2, 7----7, 8----8) or just not connected, since they're not used.

On a Gigabit cross-over, these other wire pairs ARE used, so you have to cross them over too, as follows:

1------7

2------8

7------1

8------2

If you have connectors, crimpers, and a spool of cable, this cable can be created pretty easily.

Hope this helps.

[konigl]

CORRECTION!!! PLEASE READ!!!

I had T1 cross-overs, Token Ring cross-overs, and Ethernet cabling mixed in my brain. Do NOT use those pinouts in my previous post. They will NOT work for 10/100 Ethernet or Gigabit Ethernet.

The correct ones for a Gigabit Ethernet cable are as follows:

1----3

2----6

3----1

6----2

5----7

4----8

7----5

8----4

Sorry about that.

Pins 1, 2, 3 and 6 are the ones used for 10/100 Ethernet, if you just want to make a cross-over cable for that.

10/100 Ethernet does NOT use pins 5 and 4 (but Token Ring does, along with pins 3 and 6).

Pins 1, 2, 5 and 4 are the ones used for a T1 RJ-48 connector.

Pins 1, 2, 7, and 8 are the ones used for a 56K DDS port.

Again, my apologies for posting bad information. The information in this post IS correct.

-Larry

[jcleary]

So if you use a regular crossover cable w/ 1000T GBIC it will not work?