Aaron, We use LDAP to store host information, including everything DHCP needs to build the configuration file. Four times each hour a script rebuilds the DHCP configuration from the LDAP data. Our wireless "guest" network allows anybody who authenticates to get an address via an open range.
Each campus has two or three identically configured servers and clients are directed to all servers simultaneously, via DHCP-relay on the router. This works because the DHCP server will both offer the same address for statically assigned hosts, so it doesn't matter which server responds first; and isc-dhcpd is smart enough to check if an address is in use before assigning it, via a ping IIR, for the open range. We have been doing this for about five years without significant problems. We don't sync the leases file because, by definition, leases are temporary and even MS Windows is pretty good about renewing it's lease when it needs to. On Tue, Oct 2, 2012 at 12:11 PM, Aaron Hall <aaron.h...@washburn.edu> wrote: > We're considering ways to provide redundant DHCP to maintain service > should our (physical) server go down suddenly. We're using isc-dhcpd on > RHEL. One server handles all of campus, and it's not breaking a sweat. > > Our first thought was ISC's failover, but it doesn't seem well-suited > for us. We have a large and complex DHCP config (many subnets, many > static hosts), and failover doesn't keep the configs in sync. Further, > the config changes near-constantly during the day. Our wireless network > registration system (NetReg 1.3) stuffs new registrations into the DHCP > config (via an included file). We also have concerns about how > IP pool-sharing works, but that's secondary. > > How do other shops provide redundant DHCP service when the built-in > isc-dhcpd failover isn't appropriate? > > We've planned a fairly hacky solution, but I really hope it's an > already-solved problem. Our plan is to: > > * Maintain the backup server as a hot-spare, with dhcpd configured but > not running. It won't run the registration software, just dhcpd to > maintain service to existing clients. > > * Whenever a registration event causes the master dhcpd to restart, copy > that config and the leases DB to the backup server. There's already a > cron job that checks every minute for new registrations and restarts > dhcpd if so; we'd hook into that. (The details of this are tricky -- > what happens, say, if the master server dies in the middle of a copy? > We can surmount that, but still.) > > * Should the master server go down, we'd sanity-check the config on the > backup, and turn on dhcpd. This could be a manual or automatic > process. > > I'd be grateful for pointers to other ways, or comments on the above > scheme. > > Thanks, > Aaron > > -- > Aaron Hall <aaron.h...@washburn.edu> > Asst. Systems & Network Administrator > Washburn University ITS > 785-670-2305 > _______________________________________________ > Tech mailing list > Tech@lists.lopsa.org > https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech > This list provided by the League of Professional System Administrators > http://lopsa.org/ -- Perfection is just a word I use occasionally with mustard. --Atom Powers-- _______________________________________________ Tech mailing list Tech@lists.lopsa.org https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
