Switch – Trunk fiber ports on switches

ethernetfibersfpswitchtrunk

We are planning to purchase new switches for our network. We have three buildings in the same area that are all connected by fiber. Our main building is very large and needs to be connected by fiber from north to south. North is where our core switches will reside.

My question is this: We will have three fiber connections coming into our core switches – 1 from each remote building and 1 from the south side of the plant. Can we use two switches in the north plant each with 2 fiber ports to accomodate this? This would leave 1 fiber port open. We would be trunking the two core switches by ethernet ports. Will this work ok or do we need to trunk by the fiber ports?

Best Answer

You haven't provided any info about the interfaces you're going to use with the fibre link, so I'm guessing that this is 1gbit.

If the switches you're going to use have 1gbit copper interfaces aswell then it's no problem to trunk between them, this is the normal way of connecting switches that have several uplinks.

I need to warn you however - if those core switches only have two fiber slots each then what are you going to do if one of the switches go down? Since you don't have more than 1 link to each building I highly suggest that you either get core switches with enough (sfp) ports to carry all the fiber links, or get more links between the buildings to build a ring topology - like this:

                                  HQN
                                 / | \
                                /  |  \
                               /   |   \
                              /    |    \
                             B1----B2---HQS

(Link between HQ North and Building 2 would actually be optional)

This would ensure that any single link can go down without interrupting the network. The next step would be designing STP etc, but that's out of scope for this question.

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