Fiber cores

[Jonn cos]

Hi all,

If i need to connect 2 cisco 2960S switch over fiber with over a distance of 200m, i know if have to use GLC-SX-MM but how many cores do i need ? to be honest i dont have understanding of when we need to use how many cores ?

Can someone help me understand in which case do we need 2 core or 6 core fibers ?

[Leo Laohoo · Accepted solution]

1 core = 2 pairs

So you need 1 core fibre. 

[Jonn cos]

Sir in which case do i need more then 1 core fiber from one location to other ?

[Reza Sharifi]

No sure what you mean by core, but usually the fiber count is by strands or pair.  So to connect 2 switches together you need a pair of fiber which is equal to 2 strands.

HTH

[Jonn cos]

Basically Sir, there was a discussion a while back about the design of our headoffice network. We are discussing how many core of fiber we needed from every floor to 3rd floor where the aggregation switch was placed (it was 3560 24 with SFPs). At that time our vendor told us to deploy 6 core fiber from every floor to 3rd floor for uplink purpose.

Thats why i asked,

[Reza Sharifi · Accepted solution]

Ok, I understand now.  6 cores means 6 pairs. So, you need 6 pairs of fiber from each floor to 3rd floor.  This will accommodate up to 6 connections from each floor to 3rd floor. 

Is that clear now?

HTH

[Jonn cos]

Thanks alot Reza bhai (dont mind if i call you bhai). Sir kindly correct me that always one core (or one pair) is needed for a connection to be made ?? am i right ?

[Reza Sharifi · Accepted solution]

Sir kindly correct me that always one core (or one pair) is needed for a connection to be made ?? am i right ?

That is correct.  You need a pair for one connection. In that pair, one strand is for tx and the other strand rx.

remember a pair is equal to 2 strands.

HTH

[Jonn cos]

Thanks alot sir. Kindly dont mind about my request.

[Jonn cos]

Sir i read an expert saying that you are almost an authority over VSS (outside Cisco). Can you comment on my post on 4500 SUP 8-E

[Reza Sharifi]

Sir i read an expert saying that you are almost an authority over VSS (outside Cisco). Can you comment on my post on 4500 SUP 8-E

Can you copy and paste the URL for that post?

[Jonn cos]

Sir below is the link

https://supportforums.cisco.com/message/4053603#4053603

[Reza Sharifi]

Unfortunately, I can't common about this, as this sup is pretty new, but I am sure, Marvin has provided you the correct info.

In general and I think, VSS will be supported in all Sups going forward.  Now, if it is not in the current version of software, I am sure it is on road map.

HTH

[Jonn cos]

Thanks alot sir, i hope you didnt mind

[Peter Koltl]

Let's put in writing that

• in this context "core" is not a proper term to use
• 1 core is NOT 2 pairs.     2 pairs = 4 strands.