Upgrading server hardware on existing failover pair

Oscar Ricardo Silva oscars at mail.utexas.edu
Tue Apr 3 14:43:43 UTC 2012

Thanks for the responses.  I forgot to mention that I use omshell to 
"gracefully" bring down the server and it notifies the partner. 
Whenever we need to reload for a new configuration I bring one server 
down this way, the partner is notified of the state change and goes into 

For now I'll be keeping both servers on 3.1.3.  We've written some 
patches that our developers need to check against new versions.



Message: 5
Date: Mon, 2 Apr 2012 20:58:16 +0000
From: Randall C Grimshaw <rgrimsha at syr.edu>
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: RE: Upgrading server hardware on existing failover pair
	<E026853FAE2E5E47BE78B287F89DAF9E3C18297A at SUEX10-mbx-03.ad.syr.edu>
Content-Type: text/plain; charset="us-ascii"

Technically, I think that at the time you gracefully shut down the peer, 
that you will not be in partner down mode. If you plan to be down long 
you will want to manually put the host into partner down mode or risk 
exhausting the half of your pool that is still available.
This may not affect your transition, but it is a technical issue you 
should be aware of in an outage. - self inflicted or otherwise.

Randall Grimshaw rgrimsha at syr.edu
From: dhcp-users-bounces+rgrimsha=syr.edu at lists.isc.org 
[dhcp-users-bounces+rgrimsha=syr.edu at lists.isc.org] on behalf of Oscar 
Ricardo Silva [oscars at mail.utexas.edu]
Sent: Monday, April 02, 2012 4:30 PM
To: dhcp-users at lists.isc.org
Subject: Upgrading server hardware on existing failover pair

We currently have a pair of servers running ISC 3.1.3 in a failover
configuration.  Both physical servers are scheduled to be replaced with
newer hardware and I'd like to bounce my plan off the list to be sure
it's sane.

1.  Shut down dhcpd on the secondary (gracefully).  The primary should
go into partner-down

2.  Copy configuration and leases file from old secondary to new secondary

3.  Bring up *NEW* secondary, make sure it can communicate on the network

4.  Start dhcpd on the *NEW secondary and it should communicate with the
primary and get updates

5.  Wait until both servers are in the *NORMAL* state

6.  Repeat these steps for the primary

*SHOULD* this work without an expected interruption in service?  I know
during upgrades, things can and will go wrong but I'd like to avoid the
obvious things as much as possible.


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