On Sun, Dec 22, 2002 at 10:25:53AM -0800, Rod Roark wrote: > (1) Round-robin DNS. Advertise both external IP addresses
Bind prefers the first record I believe, so this could be more than a 1/2 down if one were dead. > (2) Run a separate instance of BIND on each of the two > interfaces, one as the primary and one as the secondary > nameserver. Each instance resolves names to its own IP Ugh. This violates some RFC expectations, and might cause problems if carried to extremes (NS records). For A records it should work fine, however it's still messy. > Any other ideas? A) Use an external DNS provider that allows dynamic updates (ie dyndns.org). Have each server set to update for it's IP address. How to control this is the only question, but that's easily solved by some scripting to determine which external link is up (ping to that side's gateway, then to something farther through that link), and which servers are online (heartbeat). B) use the methods in A for detection and decision making, and update your DNS servers accordingly. This is trivial for something like djbdns, less so for BIND (debian does have a bind dynamic update tool though). By doing intelligent ping checks (packet loss > 10%) you can also take links offline if the're overloaded, the ISP is screwed, etc. For instance, I have a script that knows about all my connectivity options (ie, DSL, cable, dialup1, dialup2), and it runs through in my preferred order checking for a link that passes 100% of the packets. If it is not met, it brings up the next in line circuit. If it is met, it turns down all other methods past that. The only thing you need different is hooks into DNS... I can give more details if desired... this is a fun exercise though. This is an easily solved challenge. Doing so elegantly sounds like the interesting part... ideas? I have some, which I'll be happy to share. -- Ted Deppner http://www.psyber.com/~ted/ _______________________________________________ vox-tech mailing list [EMAIL PROTECTED] http://lists.lugod.org/mailman/listinfo/vox-tech
