Should a Metropolitan Area Network (MAN) be setup with a router at each site? Should a Metropolitan Area Network (MAN) be setup with a router at each site? Or, because the connections between sites are usually at layer two, should each site operate on one "master" switch which then interconnects them through a router at the main site. Or are both setups viable options? The specific scenario I am interested is setting up a MAN for about 5 sites, each with only about 50 users and each of the sites will be interconnected through one "main" site which will also house all the servers.

Yes. You do not want to extend Layer 2 MAN links beyond the border of each location - this is bad design for a number of reasons:

* You will extend the broadcast domain of all 5 sites up to the main site
* Layer 2 issues (STP re-convergence, broadcast storms etc) can now affect multiple sites at once
* It will not scale in the future as you bring on more sites, or have an outlying site that needs to come in over a WAN link



Now whether you use an actual router, or a layer 3 switch with a routing protocol is up to you (switches are generally a lot better price/performance for basic L3 routing, at the cost of scale and features), but the result is the same.