fiber question

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blarg

Limp Gawd
Joined
Jul 19, 2009
Messages
140
I'm looking at connecting to a private fiber connection. The installer said he wanted to pull the fiber into building 1 and run 4 strands to my head end room there and pull another 4 strands through an underground conduit to building 2.

When this gets turned on from a network layout perspective is this going to look like I have a patch cable between buildings or will it be more like my traffic is going through the whole fiber loop and comming back to the other building?

I'm trying to figgure out if I need to make a Vlan from building to building or if I can just plug the fiber in straight switch to switch using fiber modules and have it all be one flat subnet.

Thanks
 
That's not a question that anyone here can answer, it all depends on how it's getting installed. Who's doing the install? Are they going direct from building to building? If it's an ISP or Telco are they putting equipment in at either/both ends?

Short Version: Ask your installer. ;)
 
You don't want to have a single VLAN span buildings (if possible). If you must, you have two pair of fiber so create an etherchannel link between the buildings and connect it to your core using 1000Base-LX modules (I assuming it's single-mode fiber).

A more efficient but slightly more complicated layout would be to use two separate layer 3 links from the core to the access switch in the next building. Use a routing protocol like EIGRP to equal-cost load balance the two paths to the new network in the other building. You would need layer 3 capable switches for that though.
 
It's not a telco or anything where they have a project engineer. This is a 3 county loop thats owned and operated by several school districts. I have 3com super stacker layer 3 switches with SFP 1000Base-SX fiber modules.

My plan was to go directly from switch to switch with the fiber but I didn't understand how it would work with the installer wanting to pull 4 strands to each building. I could ask him to just pull a direct peice of fiber to go from switch to switch in each building. Then I can use up my last fiber module port on one of the switches and tie into the loop that way. I'm not sure if that works as easily as what I'm thinking though.
 
blarg said:
This is a 3 county loop thats owned and operated by several school districts.
Click to expand...

Again, these people know how their setup works and can tell you if you need to do anything specific.

Fibre operates in strand pairs, so pulling 4 strands in to each building is essentially giving you two 1Gb connections at each end. The configuration on your switches very much depends on how the fibre network operates- they may be doing some transparent VLANs and routing which will make it appear as if your switches are directly connected at which point you can do whatever you want. They may be doing a different setup however which will require you to change your config. I agree with matt that you want to separate subnets in each building as there is no need for all the broadcast traffic over the fibre. A few VLANs will do the trick for you there.
 
They usually pull an extra pair for redundancy also - so four strands equals one pair for production, one for backup.
 
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