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! >
