Justifiable to use Fibre

[tonywhyte87]

As some of you know, I am working on a University project designing a network. I would like to know if it is justifiable to use fibre between the core and distribution of a network with around 300 users?

Or could someone please tell me when would be a good idea to use fibre?

[darren.g]

Tony Whyte wrote:
As some of you know, I am working on a University project designing a network. I would like to know if it is justifiable to use fibre between the core and distribution of a network with around 300 users?
Or could someone please tell me when would be a good idea to use fibre? 

When you've got more money than sense, or when the distance/speed requirements demand it.

If you're running a 10 gig (or 40 gig, or 100 gig) backbone between your core and distribution layers, then fibre is almost inevitable - while you *can* get 10 gig running on copper if it's very good quality cable, the distance you can run it across is the same as gigabit ethernet on good cabling - 100 meters maximum on cat6a or cat7 cabling, 55 meters on cat6. 40 gig - forget it on copper. 100 gig ditto.

How far from the core are your distribution switches? If they're close (sub-100 meters total), and you're only running a 1 gig backbone (or port-channels in multiples of 1 gig), then forget the fibre - unless you have the money to future-proof yourself against possible 10, 40 or 100 gig backbone requirements.

If the access switches are more than 100 meters from the core switches, then fiber is a must, since you can't run copper over distances of more than 100 meters total (including patch leads).

Cheers.

[Leo Laohoo]

Fibre vs copper?  Fibre wins hands down anytime, all the time. 

[Reza Sharifi]

Usually you use fiber ports for your uplinks.  Lets say you have a bunch 3560 switches with 48 port or 24 copper ports and 2 10Gig fiber ports. So, in this case most people use the copper to connect to end devices and fiber for uplinks to distro, core, etc...One good reason for doing this is because you uplink pipes (10 Gig ports) can carry a lot more bandwith than if you were to use 1Gig for uplinks.  Now, can you use copper ports for uplinks, sure, if the distance is within the copper specs and you don't have extra funding for fiber optic cable and optics, you could simply justify using copper.

HTH

[Joseph W. Doherty]

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Posting

Sure fiber can be used, and often is, problem though is its extra cost, both for the ports and the optics modules.

BTW, for just 300 users, not quite sure why you would need both a distribution and core layer.  In fact, on a 6509, 7x48gig provides 336 gig ports; pretty close to all ports at wire-speed.  I.e. you could run all 300 users on one box, of course, unlikely all 300 users would be within copper distance.