Fixing failover mistakes

Jason Frisvold frisvolj at
Sat Nov 14 19:39:07 UTC 2009

Hash: SHA1


	Can someone explain the MCLT parameter to me?  We currently have DHCP set up in a failover configuration, though the config is somewhat incorrect.  I need to make changes to the configuration to resolve this, but I think I'm running into problems with the MCLT parameter.

	I've replicated our setup in the lab and attempted to change the name of one of the failover peers so they are identical on both machines.  Once completed, the servers go into a recover-wait state.  From what I'm observing, new DHCP leases are not handed out until the servers move back to normal state.  After some googling around, I came across this passage :

"After the server in RECVER state has received the UPDDNE message, it moves into the RECVER-WAIT state. The RECVER-WAIT state
exists to let the recovering server wait until the MCLT has expired before it begins serving DHCP clients. This allows any leases
that the recovering server may have assigned after it lost contact with the other server to expire. This is importatnt when the
recovering server is being restored as a result of an incident that caused it to lose its database. In cases where the recovering
server has been down longer that MCLT, this waiting period is not required."

If I'm reading this right, I'll need to wait until the MCLT time expires before the server will move back to normal state.

Is there a way to handle this manually and force the servers back to a normal state?  If, perhaps, I delete the dhcpd.leases file on the secondary, can I lower the MCLT temporarily to reduce the time I have to wait?  Or will this cause data loss?

If data loss is an issue, what if I disable the secondary server for a period of time greater than the MCLT, then try the above?  Will that resolve any data loss issues?


- ---------------------------
Jason Frisvold
Network Engineer
frisvolj at
- ---------------------------
"What I cannot create, I do not understand"
   - Richard Feynman      

Version: GnuPG v1.4.8 (Darwin)


More information about the dhcp-users mailing list