Hi, Thank you for a good description. But what's your problem there now? You receive x.y.z.0/24 from Router1 and send it to Router2. What do you want to achive and are missing?
On Fri, Jan 18, 2019 at 9:13 PM Roman Romanyak <[email protected]> wrote: > > Alexander, thank you for your feedback. > > Here is a diagram: > > [ ISP1 ] [ ISP2 ] [ ISP3 ] [ ISP4 ] > | | | > | > | | | > | > [ Router 1 ] [ Router 2 ] > | | > | | > [ Layer 2 Switch ] > | > | > [ Bird Route Server ] > > > Router 1 and 2 do not peer directly. There is OSPF running, so all nodes > learn a route to other nodes connected interfaces. > Both routers peer to route-server and are route reflection clients. > > There is a route x.y.z.0/24 coming from from each ISP. Router 1 chooses ISP2 > (because of as-path), what path Router 2 is choosing doesn't matter. > > I need to force traffic to x.y.z.0/24 via ISP1. > In order to do that, I'm matching the route x.y.z.0/24 in the import filter > on the route-server (maching a route itself and also ISP1 ASN in the path) > and setting the local preference to 150. > Then this route is re-advertised to Router 2, which will select it as best, > because of iBGP and high local-preference. The route is not announced back to > Router 1, because it came from there. > > An alternative way, to do that is to mach a route on Router 1, increase a > local-pref there and that route will be leared by router 2 through the > route-server. But I'd like to do that on route-server to use a centralized > place for these kinds of things. > > Here is a show route output from a route server: > > > bird> show route for x.y.z.0/24 all > x.y.z.0/24 via 10.1.1.65 on em2 [edge_r1 18:25:09] * (100/11) [AS123i] > Type: BGP unicast univ > BGP.origin: IGP > BGP.as_path: 111 888 333 999 > BGP.next_hop: 1.1.1.1 > BGP.med: 0 > BGP.local_pref: 150 > via 10.1.1.65 on em2 [edge_r1 2019-01-17] (100/11) > [AS123i] > Type: BGP unicast univ > BGP.origin: IGP > BGP.as_path: 222 777 999 > BGP.next_hop: 2.2.2.2 > BGP.med: 0 > BGP.local_pref: 100 > via 10.1.1.66 on em2 [edge_r2 2019-01-16] (100/11) > [AS123i] > Type: BGP unicast univ > BGP.origin: IGP > BGP.as_path: 333 666 999 > BGP.next_hop: 3.3.3.3 > BGP.med: 0 > BGP.local_pref: 100 > via 10.1.1.67 on em2 [edge_r2 2019-01-17] (100/11) > [AS123i] > Type: BGP unicast univ > BGP.origin: IGP > BGP.as_path: 444 555 999 > BGP.next_hop: 4.4.4.4 > BGP.med: 0 > BGP.local_pref: 100 > > bird> > > > > > > > On Fri, Jan 18, 2019 at 2:17 PM Alexander Zubkov <[email protected]> wrote: >> >> Hi, >> >> I do not completely understand your setup. You better show route >> tables from all the routers and what is announced in which direction. >> >> > So I get the desired effect on the second router, it will learn and >> > install a route with high local pref. The first router where the desired >> > transit link is connected by default selects another transit link because >> > of the shorter as-path. >> >> How this could happen? If you got this route on the route reflector >> from the first router, than it should have this route in the required >> direction. If it had this route to another transit link, it would >> announce this to the route reflector. There is no reason to propagate >> the routes back to the peer, because they are already there.I think >> you can do some tricks, but first we need to understand what do you >> want to achieve. >> >> On Fri, Jan 18, 2019 at 7:23 PM Roman Romanyak <[email protected]> >> wrote: >> > >> > Hello Bird users, >> > >> > Does anyone know if there is a way to announce a BGP route back to the >> > router it was received from. >> > I need to do this for the following scenario. >> > Lets say there are two routers with 2 transit links on each with full view >> > tables and Bird server as a route-reflector. There is a need to force >> > traffic to a specific destination via one of the ISPs, so I match the >> > route in the import filter and set a local pref on it. But that will only >> > make the route server announce the route with a high local pref to a >> > second router, where the desired transit isn't directly connected. So I >> > get the desired effect on the second router, it will learn and install a >> > route with high local pref. The first router where the desired transit >> > link is connected by default selects another transit link because of the >> > shorter as-path. >> > >> > Here is the import filter snippet (x.y.z.0/24 is a dest route, as-path >> > 1234 is a directly connected ISP on router-1: >> > >> > if source = RTS_BGP && net = x.y.z.0/24 && bgp_path.first = 1234 >> > then { >> > bgp_local_pref = 150; >> > accept; >> > } >> > >> > I think that bird doesn't do that because the protocol matches on the peer >> > and on the route. >> > >> > >> > Thanks!
