5

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.

6

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.

  • Thanks, that makes a lot of sense. I hadn't considered the broadcast domain and was getting myself wound up over the limited MAN documentation. – Jason Mar 29 '18 at 11:51
  • yeah - MAN doesn't really describe a technology or an architecture, just a coverage area - searching Metro-Ethernet is probably where you'll find the most information, but most of that info is from the carrier's perspective, and very much L2 everywhere – Benjamin Dale Mar 29 '18 at 14:14

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.