In that case multihop BFD (if supported on both sides) would really help. Regards, Jeff
> On Nov 28, 2015, at 11:37 AM, Matthew Petach <mpet...@netflight.com> wrote: > > One thing I notice you don't mention is whether your > BGP sessions to your upstream providers are direct > or multi-hop eBGP. I know for a while some of the > more bargain-basement providers were doing eBGP > multi-hop feeds for full tables, which will definitely > slow down convergence if the routers have to wait > for hold timers to expire to flush routes, rather than > being able to direct detect link state transitions. > > Matt > > > On Sat, Nov 21, 2015 at 5:44 AM, Baldur Norddahl > <baldur.nordd...@gmail.com> wrote: >> Hi >> >> I got a network with two routers and two IP transit providers, each with >> the full BGP table. Router A is connected to provider A and router B to >> provider B. We use MPLS with a L3VPN with a VRF called "internet". >> Everything happens inside that VRF. >> >> Now if I interrupt one of the IP transit circuits, the routers will take >> several minutes to remove the now bad routes and move everything to the >> remaining transit provider. This is very noticeable to the customers. I am >> looking into ways to improve that. >> >> I added a default static route 0.0.0.0 to provider A on router A and did >> the same to provider B on router B. This is supposed to be a trick that >> allows the network to move packets before everything is fully converged. >> Traffic might not leave the most optimal link, but it will be delivered. >> >> Say I take down the provider A link on router A. As I understand it, the >> hardware will notice this right away and stop using the routes to provider >> A. Router A might know about the default route on router B and send the >> traffic to router B. However this is not much help, because on router B >> there is no link that is down, so the hardware is unaware until the BGP >> process is done updating the hardware tables. Which apparently can take >> several minutes. >> >> My routers also have multipath support, but I am unsure if that is going to >> be of any help. >> >> Anyone got any tricks or pointers to what can be done to optimize the >> downtime in case of a IP transit link failure? Or the related case of one >> my routers going down or the link between them going down (the traffic >> would go a non-direct way instead if the direct link is down). >> >> Thanks, >> >> Baldur >>
