> -----Original Message----- > From: fedora-list-bounces@xxxxxxxxxx > [mailto:fedora-list-bounces@xxxxxxxxxx] On Behalf Of Benjamin Franz > Sent: Wednesday, August 31, 2005 2:42 PM > To: For users of Fedora Core releases > Subject: Re: OT: DNS Failover > > On Wed, 31 Aug 2005, Mike McGrath wrote: > > > I'm curious about how others in the Fedora community are doing DNS > > failover. Specifically I have two sites, one primary (in a large > > city) and one secondary (out in the middle of nowhere). > The idea is > > that we'd host DNS out of the secondary site to use the web > servers in > > the primary site. > > > > My question is how are people handling outages at the main > site. If > > the primary site burns down or all the servers get stolen or > > something, is my only option a manual of the configs to > point from one to the other? > > Slightly different than what you are asking, but we > multi-home our servers and placed a DNS server in each IP net > that returned _only_ the addresses for that subnet with a 900 > second TTL. If we experience loss of IP on one pipe, that > renders the appropriate DNS server immediately unreachable > leaving only the good pipe's addresses being returned on > fresh queries while the stale unreachable addresses will > expire within 15 minutes. > > This has worked very well for us in practice since the only > people impacted by a loss of a pipe are those who were > actually browsing our website servers via the down net in the > few minutes before the network outage while lettings us get > the good routing of being in two large tier-1 ISP routing > blocks (IP blocks of less than roughly a /18 just don't get > good routing IME because of backbone routers dropping small > subnet routes). > > The problem with browsers caching IPs until the browser is > killed is not fully soluble via any DNS based system. > > You can trade that for a portable block of IP addresses and > broadcast your routes, but you wil take a hit on normal > routing of a small subnet and on the reconvergence time of > routes after any failure. > > There are no perfect solutions to this issue, AFAIK. Every > solution will have some failure mode that will impact you > more or less depending on your own requirements. > > -- > Jerry > > Simple things should be simple, complex things should be possible. > - Alan Kay > > -- > fedora-list mailing list > fedora-list@xxxxxxxxxx > To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list > > Thats an interesting way of doing it. I'll have to test that out too. Thanks everyone for your comments. -Mike
