On 2022-06-27, Ivo Chutkin <open...@bgone.net> wrote: > Hello guys, > It is not related to OpenBSD. Since I started my admin "career" with > OpenBGPD and OpenBSD, I just need some thoughts and advises from anyone > more experienced. > > The situation is as follows: > I have 2 border routers in main location. All Upstreams,IX-es and > clients have eBGP sessions. Clients are mostly small regional ISPs. > We carry customers traffic from main location to their region over L2 > vlans. On all regional POPs, I have L3 switches (Brocade ICX6650). > > The idea I have is to make eBGP session with regional ISPs on their > local POP switch and distribute their prefixes to other ISPs connected > there. To make some kind of Internet Exchange on regional level or even > national level for our customers. > > As far as I know, all routers (BGP running switches) in a single AS, > should be connected via iBGP (If I am not mistaken, it is called full > mesh). But, on main routers, I have number of full feeds that regional > switches are not capable to handle. > > Do you think it could be done somehow without iBGP full mesh or it is > stupid idea by design?
You do want either full mesh or to use route reflectors, but you don't need to send a full BGP table to all the routers, you can filter in various ways (for example, maybe just carry national routes, or peer routes, or routes with a short AS path length, or...there are lots of options). But you do need to make sure that other destinations are still reachable from routers receiving a partial table so in that case you will want to generate/announce a default route; probably arrange your filters so that the default route is only sent/accepted on those routers with a partial table - for the full table routers you'll usually want _no_ default route so that packets for nonexistent destinations get "net unreachable" rather than maybe flip-flopping between a couple of routers which point default to each other. -- Please keep replies on the mailing list.
