On Thu, May 2, 2013 at 12:31 PM, Michael Mol <mikemol at gmail.com> wrote: >>> with its default gateway pointing toward the ISP handling it. DNS >> service is simple enough to have standalone servers for each instance >> you need. > > This would also require either resources or underlying authorizations I > don't have. CentOS VMs are really, really cheap.... >> Web browsers are actually very good at handling multiple IPs in DNS >> responses and doing their own failover if some of the IPs don't >> respond. > > It varies greatly by client software. And given the explosion of > unreliable network connections (wifi, mobile), some of that failover > logic's margin is already lost in dropped packets between the client and > their local network gateway. Yes, but typically they can deal with receiving multple IPs from the initial DNS lookup even if some are broken better/faster than getting one IP which subsequently breaks and then having to do another DNS lookup to get a working target. At least the few broswers I tested a while back did... >> For other services you might need to actively change DNS to drop IPs >> if you know they have become unreachable, though. > > Yup. That's what I was planning on doing, more or less. Start with > ordering IPs by route preference, drop IPs by link state. I just wish I > could drive it by snooping OSPF... I don't think you can count on your ordering reaching the clients or meaning anything to them if it does. And some applications won't ever do a lookup again. -- Les Mikesell lesmikesell at gmail.com