mclt Values, was 2 Instances of dhcp on Same Platform

[Martin McCormick]

Thanks for your reply.  There is a lot to think about here.
I wouldn't have dared do the SIGTERM in my script because I
figured I'd end up in a recover-wait state for both servers for
30 minutes.  That would certainly make the telephones ring around
here.
Glenn Satchell writes:
> I move from normal to communications-interrupted
> 
> Note the primary goes into communications-interrupted, not partner-down.
> Restart the secondary.

________________________________________________________________________________

> So, the question is, what effect does your clean shutdown to
> partner-down have? The dhcpd.conf man page is not exactly clear on
> this, but maybe the switch to partner-down triggers the wait until MCLT
> passes? When it is communications-interrupted it does not wait because
> the remaining server cannot hand out any leases for the other server's
> address ranges. I think a change to the script so that it doesn't
> switch the remaining server to partner-down might work better.

	That makes sense to me.

> As for the multiple instances of dhcpd, in the dynamic pools you need a
> way to deny the fixed-address clients. Otherwesie they could be given a
> dynamic address. Unless you can come up with some sort of generic class
> to do that, you are going to need to update both sets of dhcpd.conf
> files with information about the static hosts, and this negates what
> you're trying to do.
> 
> Alternatively what about using omapi to add/delete the fixed-address
> host entries?  This avoids the server shutdown issue completely.

	When I first read about omapi, that was the very first
thing that crossed my mind.  In the man page for dhcpd when
discussing omapi, however, I read this:

->THE LEASE OBJECT
->       Leases  can't currently be created or destroyed, but they can be looked
->       up to examine and modify their state.
->
->       Leases have the following attributes:
->
->       state integer lookup, examine
->	    1 = free
->	    2 = active
->	    3 = expired
->	    4 = released
->	    5 = abandoned
->	    6 = reset
->	    7 = backup
->	    8 = reserved
->	    9 = bootp

	Along with the dhcp ranges, our dhcpd.conf file contains
a bit over 8,400 static entries like:

host helium.cis.okstate.edu {
 hardware ethernet 00:60:08:37:7F:0A;
 fixed-address 10.6.200.97;
} #end entry for helium.cis.okstate.edu

	The comment after the } is a little automatic tag I
generate in the script (actually a C monster) that populates each
subnet with appropriate hosts.

	If omapi can add and delete those dynamic entries, I can
certainly revise what our home-grown IP-number management system
does and it would end up actually being much less complex than it
is now.  We rarely ever would need to bring either server down if
we could use omapi to add and delete those static addresses.

	This wouldn't be the first time I have misinterpreted
documentation, but it isn't the fault of that documentation.
If you can use omapi to continuously make static adds and deletes,
do they end up in dhcpd.leases?  If so, I could write a master
load script that puts them there and then leaves them out of
dhcpd.conf.   I assume many other sites have the same issues, but
I do apologize for the length of this message.

Many thanks.

Martin McCormick WB5AGZ  Stillwater, OK 
Systems Engineer
OSU Information Technology Department Network Operations Group