But than it'll be replaced on the router1 and it will withdraw the announce, and so on...
On Mon, Jan 21, 2019 at 7:38 PM Roman Romanyak <[email protected]> wrote: > > I'd like to do a route manipulation on the route server and send a route back > also to router1 with a local pref via ISP1. > > On Sat, Jan 19, 2019 at 2:43 AM Alexander Zubkov <[email protected]> wrote: >> >> 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!
