This is a “unanswerable” question. In honesty, you can have 20k routes in OSPF and it be responsive so the routing platform does not have a limit. The number of routers, is another issue, if you have 500 routers all fiber connected and they don’t go up/down much, then no big deal, however, if they do go up down quite a bit or you don’t know how to manage them, then yes this can be a factor. The last thing is convergence time, if you have lots of fiber, and/or well connected routers, then that is not a major issue, break part of your network and see how long it takes for a reroute, if that is acceptable, then again no worries.
Now OSPF books, state that you should have no more than 75-100 routers, but I have read things that state no more than 50 and I have other networks that have more than 500. So.. Again, it’s not a good answerable question. However, my suggestion is to look at your network as a whole and see if there is some kind of logic, to splitting up your OSPF domains. You can use OSPF areas, or you can use BGP between them. But there needs to be a good, constant method to splitting your network like that. Keep in mind that using defaults will cause traffic to shift, etc, so you need to plan plan plan… Just my two cents. Dennis Burgess, Mikrotik Certified Trainer Author of "Learn RouterOS- Second Edition” Link Technologies, Inc -- Mikrotik & WISP Support Services Office: 314-735-0270 Website: http://www.linktechs.net<http://www.linktechs.net/> Create Wireless Coverage’s with www.towercoverage.com From: Af <af-boun...@afmug.com> On Behalf Of Brough Turner Sent: Thursday, June 7, 2018 1:41 PM To: af@afmug.com Subject: [AFMUG] OSPF - How large can a flat network grow? We're an urban WISP with a dense mesh of wireless links and a router per building. I am concerned that, without paying attention, we have grown to 600+ routers and ~2550 routes in one OSPF domain. This network has a diverse mix of routers from CCR1036s down to RB750UPs. We're not having any OSPF problems at this time and I have plenty of other things to worry about, but I'd hate to hit some limit and have the whole thing blow up. Does anyone have experience (positive or negative) with large flat OSPF networks? And, if you have had problems, what were the problems? Thanks, Brough Brough Turner netBlazr Inc. – Free your Broadband! Mobile: 617-285-0433 Skype: brough netBlazr Inc.<http://www.netblazr.com/> | Google+<https://plus.google.com/102447512447094746687/posts?hl=en> | Twitter<https://twitter.com/#%21/brough> | LinkedIn<http://www.linkedin.com/in/broughturner> | Facebook<http://www.facebook.com/brough.turner> | Blog<http://blogs.broughturner.com/> | Personal website<http://broughturner.com/>
