LC to LC connection from switch to switch inbetween Patch Panels

[mahesh18]

                   Hi all,

Need to confirm  Fibre optic connections.

Laying Fibre from Switch to switch both sides take SFP and it is LC to LC connection.

IT goes via 2 fibre patch panels.

A side

Switch to Patch panel

LC cable has has two colors Red and Black.

Side 1

LC cable info   Fibre to Fibre both ends

Red is A

Black is B

Other side of LC cable

Black is A

Red is B

IF i trace cable Red A side it is same but goes to Black B.

So should i plug the cables same from switch to patch panel step 1

Step 2  Patch panel  to switch same as it is  or should i need to swap end?

thanks

mahesh

[smehrnia]

Hi,

General knowledge : in fiber connections you should maintain a Cross (RX/TX) end to end connection.

your patch is straight, then the RED-to-BLACK and BLACK-to-RED (Cross format) is the correct cable format to use.

by the way, use UDLD on your fiber ports on both sides, to identify any potential unidirectional problems.

(router_if)#udld port aggressive

plz Rate if it helped.

Soroush.

[mahesh18]

Hi Soroush,

Thanks for reply back.

When you say Patch panel does the crossing does it mean that if cable Red is A on patch panel then other end of patch

should be Black A?

So this is what crossing means?

When you say Patch is straight  then does it mean that from switch 1  Red  end goes to  Black end of Patch Panel 1?

Thanks

MAhesh

[smehrnia]

Look, at the end you have to achieve a RX-TX / TX-RX format, i donno how is ur patch installed now, but usually it is like patches are straight and the CABLE itself is Cross. at the end RX should go to TX in each side.

if you use UDLD as i told you, in case of misconfig. it disables the port and you will know connection is faulty and can re-orient it.

plz Rate if it help

Soroush.

[mahesh18]

Hi Soroush,

Thanks for reply.

How can we tell if fibre is cross

will cross fibre like this

Side 1  has

Red  Aand black B

Side 2 has

A Black and B as red?

Is this cable crossed?

Thanks

[smehrnia · Accepted solution]

let me draw something for you better understanding and avoid confusion for both of us

you should use a CROSS format cable. and activate UDLD on both sides.

plz Rate if it helped.

Soroush.

[Reza Sharifi · Accepted solution]

Hi Mahesh,

In addition to what Soroush provided, you usually have 2 strands of fiber cables that make up a pair.  If you connect both sides of the cable to your switches and the link light does not come up, you can simply switch the strand around at one side of the connection and that should bring up the interface, provided the fiber is good, the patch panel is good and the port is not shut.

The most common type of fiber patch connectors for networking devices are: SC, which is used with X2 optics and LC which is used With SFP interfaces. There are also ST and MTRJ, but not commonly used in networking.

HTH

[mahesh18]

Hi Soroush and Reza,

MAny thanks for explaining me in so detail with diagram.

Regards

MAhesh