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Re: Bind Redundant master server for single zone file.



Hi !


Ian Forbes wrote:

On Wednesday 22 June 2005 15:29, Ian Forbes wrote:

Is it possible to setup two bind servers such that they can both be
"master" for the same zone, and update each other as a master would
update a slave when ever the zone file is modified?

After much thought and investigation (and not too much sleep) I have come up with three options:


OPTION 1: The "right" way.
[...]

OPTION 2: The "kludge" way. (It should work - particularly as the servers will not go down very often - but it won't scale)

- Set up two "master" servers using bind.
- Modify Dhis to run "nsupdate" to update both servers each time an IP is updated. It can be set to use tcp instead of udp for reliability. - Monitor the return codes from nsupdate, and set a "dirty" flag if the update fails. This normally means the other server, or the network is down or the other server has crashed. - Run a period script which checks for the presence of a "dirty" flag, that the other server is and that it is ping-able. - When all of these test are true, restart the Dhis server. - This will force all clients to log in again and resubmit their latest IP's, which in turn will be propergated onto both servers. (This is not as expensive as it seems as each client runs a "ping" process every minute anyhow.)


OPTION 3 <grin>: [...]
Option 4:

- setup 3 Domain Technologie Control server, go in "Backup NS and MX" of the master, and setup your slaves DNS servers authorization (login, password and ip check) - go in the "Backup NS and MX" of all your slave servers, setup URL of the master server (with login and password)
- that's it, you are done.

More or less it's what you say in option 2, except that it does scale.

If you like, you can do that on both ways, so when you add a domain on server2, it's added to server 1 and the opposite way around too. Server domain listing is exchanged using HTTPS, ip check, and triggered each 10 minutes (a server informs another one that domain listing has updated and that it should invalidate it's cache). If you do it the right way, your main server will have DNS queries only from your outside world (that's what I did, so my bind on my main server replies "unauthorized query source" for all the outgoing UDP requests).

Hope that helps...

   Thomas

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