Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Connecting 3560 Catalyst switches: fibre or CAT5e?

Hi,

Sorry, I am Cisco newbie but I need some help here:

I have a small network environment with one layer 3 Catalyst 3750 and two Catalyst 3560s running VLANs across them. All switches are placed in the same network rack.

There is some debate about how best to connect them together:

a) with LC fibre cables and SFP fibre adapters.

b) with CAT5e cables and SFP Gigabit adapters.

c) with Cisco Interconnect cables (but unfortunately we already have a bucket load of SFP gbic adapters, so I'd rather use them if possible).

Obviously the fibre SFP adapters and cables are a lot more expensive than the CAT5 equivalents and the interconnect cables.

My questions is:

1) Is there any benefit of using fibre to interconnect them over such a short distance? (they're located above/below each other in the same rack!). If so, what are the benefits?

My understanding is that fibre really only offers better latency which is important over longer distances, and the SFP ports are gigabit no matter if you use fibre or CAT5e the speed is the same - therefore I can see no point in interconnecting them with fibre - but then again, I am not a Cisco expert.

Help much appreciated!


Thanks,

Marc.

Everyone's tags (2)
2 ACCEPTED SOLUTIONS

Accepted Solutions

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

Hi,

Fiber is always better than copper in terms of being less propense to interference.

Fiber is more expensive and difficult to implement than just CAT5 cables, but if you have the fiber already, go for it.

Federico.

Hall of Fame Super Gold

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

The use of fibre optic against Cat5e began to become popular when used to span different floors and/or building.  Unlike Cat5e which has a limit of 100 metres, specific fibre optic cables can go from short range (multi-mode) to long range (single-mode). Now if budget permits, I would always choose uplinks or inter-connection to be fibre optic over copper (Cat5/Cat5e or Cat6).

If fibre optic isn't feasible then get Cat6 instead.

9 REPLIES

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

Hi,

Fiber is always better than copper in terms of being less propense to interference.

Fiber is more expensive and difficult to implement than just CAT5 cables, but if you have the fiber already, go for it.

Federico.

New Member

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

We don't have the fibre already - a consultant would like me to buy the fibre SFPs & cables whereas I would prefer to simply use my existing RJ45 gbic adapters and CAT5e cables to connect the switches.

Actually I just read that the Cisco interconnect cables are "2 pair shielded cabling" - also not fibre.

So is there best a practice, or any other benefit to using fibre other than being less prone to inteference?

If not, I think I'll just connect them with CAT5e and be done (I don't imagine there is much in the way of electrical intereference in such a small server room).

Thanks for the quick reply!

Marc

Hall of Fame Super Gold

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

The use of fibre optic against Cat5e began to become popular when used to span different floors and/or building.  Unlike Cat5e which has a limit of 100 metres, specific fibre optic cables can go from short range (multi-mode) to long range (single-mode). Now if budget permits, I would always choose uplinks or inter-connection to be fibre optic over copper (Cat5/Cat5e or Cat6).

If fibre optic isn't feasible then get Cat6 instead.

New Member

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

But thats my point - there would only be a benefit using fibre if my switches were placed a long distance apart.

As it is, a 10cm cable can link them - over such a short distance, I still haven't understood the benefits of using fibre over CAT5e/6!

Fibre optic is feasible, but I am trying to understand if it's $2500 "more beneficial" to us (thats the cost of buying fibre SFPs and cables). And at the moment I can only see 2 benefits - i) fibre is less prone to intereference and ii) it's more suitable over longer distances.

Over the 10cm between my switches, I can't see either of the above 2 points being valid.

Or am I missing something?


Thanks for input!! Its much appreciated!

Marc

Hall of Fame Super Gold

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

We always use fibre optic for uplinks.  One of our reason is neatness.  Another is the use of the ports.  Why bother using SFP ports?  If I was to interconnect using copper, I'd settle for 2960 series of switches.

If you are undergoing alot of doubts and confusions, go to the simplest ones.  Go copper.  In the future if you really see the need to go fibre optic then do what you have to do. 

New Member

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

"We always use fibre optic for uplinks.  One of our reason is neatness.   Another is the use of the ports.  Why bother using SFP ports?  If I was  to interconnect using copper, I'd settle for 2960 series of switches."

Interesting point.

We use the SFP ports basically so we can interconnect at 1gb and connect our key servers etc at 1gb. We also have the option of using etherchannel when needed. Probably not all necessary in a small office, but because the SFP ports are there we make use of them (and gbic SFP RJ45 adapters are relatively cheap).

As to why we simply dont buy the 2960 series;  I can't really say. We've been blindly following the recommendations of our network consultants - although in most of our other offices we commonly expand and lay fibre between floors/offices etc - in which case we find the SFP ports on the 3500 series useful. We also may have a system that requires a gigabit port, in which case at least we have some available without buying an entirely new gigabit switch.

Can you explain what you mean by "neatness" though? It's an interesting point.

I am glad I asked these questions though - you've raised some interesting points that a novice like me has found extremely useful! So thank you!

The more questions I ask though, the more I question what we've done with our network before!! ArghhhH!!

Hall of Fame Super Gold

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

I don't know how to make this succinct but this are what's on my mind:

1.  I used to work in a very big organization where everything had to go through "bean counters" (aka accountants).  They can't tell the difference between a computer and a calculator but, hey, management says everything have to go by them.  The first question they'll always ask is this:  Why do you want to spend 2 million dollars to make 5 million.  Can you do it for less?  Similar case, they always nit-pick our Bill of Materials (BoM).  Why do we like to design something with SFP instead of using copper?   Our reason are:  Fibre looks neater (more professional looking) as compared to using copper for uplinks, there are speeds fibre optics can do copper just won't.   Finally, they gave up.  And we got what we've always designed.

2.  I don't know why but there's always something about the way fibre optic cable that a number of us consider neat.  I mean they are not so think as copper nor can you bend fibre optics into sharp right-angles but when you are looking from a poorly taken picture, fibre optic easily stands out and quickly identified.

3.  We've got <900 switches in our network.  Some are just adjacent to each other but on a case-to-case basis, I don't mind using copper for uplinks.  Otherwise, we stick to fibre optic.  Don't know why.  Maybe it's force of habit.

Some of my reasons may be "shallow" but to even things out consider the "cons" for using fibre optic:

1.  Cables have limited "bend" limit.  Bend it too much and the glass inside might break.
2.  Cables are expensive and modules are equally expensive.
3.  Avoid mixing fibre optic cables and copper cables in the same cable managment.  Why?  See comment #1.

It's good you're asking.  You may be a novice but you sure are asking alot of questions and not just blindly follow what the contractors are saying.

At the end of the day, the network belongs to your company and not the contractors.  At the end of the day, the contractors make recommendations but you guys have to write the check.  I'd recommend that you stick to your initial choice of copper.  If you are wrong, then it's as easy as writing a purchase order for fibre optic cables and modules, right?

New Member

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

Yep! You hit the nail on the head! If we need fibre in future, I'll buy them then!

It's great feedback and definitely given me a few things to think about.

Really, in small environment like this remote office I am dealing with, it sounds like it comes down to personal preference.

And seeing as my company is pushing me to save money currently, and the fact that the switch alone cost $3000, I think I'll save the extra $2500 on fibre SFP adapters and cables and simply use the RJ45 SFP adapters that I scavenged from another office and interconnect the switches using CAT.

And in future I'll go one better and avoid SFPs altogether by using the shiny Cisco Interconnect cables!

(hey, they look neat like fibre and the cost of 1 is half the price of a pair of SFP gbics!  ).

Massive thank you for the assist & wealth of info. Highly appreciated!

//Marc

Hall of Fame Super Gold

Re: Connecting 3560 Catalyst switches: fibre or CAT5e?

Glad to be of help and thanks for the ratings. 

4548
Views
0
Helpful
9
Replies