Hello William! An ARP Controller to compose a L2 Cluster solution seems a good Idea to a begging... (I would include ND)
I will try to think a bit on that... Any suggestions are welcome. Em qui., 1 de jul. de 2021 às 16:06, William Herrin <[email protected]> escreveu: > On Thu, Jul 1, 2021 at 11:05 AM Douglas Fischer > <[email protected]> wrote: > > I'm looking for solutions do deploy some type of selective high > availability and load balance based on the glue between Layer 2 and Layer 3 > (ARP or ND). > > Hi Douglas, > > Anycast is where you send to one network address and the "nearest" > single server with that address receives the packet. > > By definition, every piece of equipment in an L2 broadcast domain is > exactly one hop from every other -- no equipment is "nearer." So > conceptually, there is no anycast. > > However, L2 domains aren't built with hubs any more; they're built > with switches. There actually are variable distances between > equipment, they're just not expressed in the protocols. So, in theory > you could build an SDN controller for your switches which sets up > different FIB entries in each switch to select which port receives the > traffic for the designated "anycast" mac address. But you may face > limitations where the hardware can't reasonably be programmed to give > each port its own FIB allowing fine-grained control of which client > reaches which server. > > Realistically... that approach would tend to be both expensive to > build and very brittle. There's almost certainly a better way to > accomplish your goal than trying to invent L2 anycast. > > If you're load balancing IP traffic, another approach might be a > custom ARP controller which responds to ARP requests with different > MAC addresses depending on the request source. There's no guaranteed > timeout for ARP bindings but if you shared around a pool of MAC > addresses guaranteeing that every MAC address in the pool gets > assigned to a currently-working server it could work. You just have to > keep in mind that gratuitous arp absolutely would not work in this > sort of scenario so you have to have a plan for switching loads > between servers without it. > > I don't think anybody has built that sort of arp controller (at least > I haven't heard of one) so you'd have to invent it yourself. > > From what I understand of EVPN, it's about creating something > equivalent to VLANs across a distributed virtual server > infrastructure. Basically like what Amazon does under the hood for its > virtual private cloud. Since you're trying to get the machines to > appear on the same subnet, not separate them to different subnets, I > don't think it's what you're looking for. > > Regards, > Bill Herrin > > > -- > William Herrin > [email protected] > https://bill.herrin.us/ > -- Douglas Fernando Fischer Engº de Controle e Automação
