Partner Down State

[Waqas Asghar]

Hi Greg


Thanks for your reply.


I am operating "Internet Systems Consortium DHCP Server 4.2.1-P1".


How can I use the features that you have mentioned in your reply ? Also regarding the second option what exactly do you mean by "lease rewind" ?


Regards,
Waqas Asghar




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Subject: dhcp-users Digest, Vol 73, Issue 22


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Today's Topics:

   1. Partner Down State (Waqas Asghar)
   2. Re: Partner Down State (Gregory Sloop)


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Message: 1
Date: Fri, 28 Nov 2014 02:36:36 -0500
From: Waqas Asghar <waqas.asghar at aol.com>
To: dhcp-users at lists.isc.org
Subject: Partner Down State
Message-ID: <8D1D8F52CC643F5-7B8-28932 at webmail-vd010.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"

Hi


I am operating two ISC DHCP servers as active/backup.
However during an outage I would like to operate the backup server in "partner 
down" state so that it can utilize all the IP's.Any suggestion how can I 
manually place the backup server in partner down state.I have checked there is a 
script that can be used but that's not working for me will appreciate it someone 
can help me out here.



Regards,
Waqas Asghar



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Message: 2
Date: Thu, 27 Nov 2014 23:46:54 -0800
From: Gregory Sloop <gregs at sloop.net>
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: Re: Partner Down State
Message-ID: <1386419988.20141127234654 at sloop.net>
Content-Type: text/plain; charset="iso-8859-15"



Hi 

I am operating two ISC DHCP servers as active/backup.
However during an outage I would like to operate the backup server in "partner 
down" state so that it can utilize all the IP's.Any suggestion how can I 
manually place the backup server in partner down state.I have checked there is a 
script that can be used but that's not working for me will appreciate it someone 
can help me out here.


Regards, 
Waqas Asghar


There's a new option in, IIRC, 4.2.0+ "auto partner down" that should do what 
you want.
However, be *very* careful with it. There are reasons that the partners might 
not be able to reach each other, and thus not really be down - and both servers 
will then assume they have the whole IP block to lease from and will be issuing 
duplicate leases all over the place. As you can imagine, this would be a very 
bad(tm) situation. So, use it carefully and consider things carefully.

There's also another option that is also in 4.2.0+ that will allow the remaining 
partner to "rewind" leases issued by the partner and "re-lease" them - thus 
giving the remaining partner a lot more endurance. It's also a lot safer than 
the "auto partner down" directive. 

From the release notes for 4.2.0a1
---
- An optimization described in the failover protocol draft is now included,
  which permits a DHCP server operating in communications-interrupted state
  to 'rewind' a lease to the state most recently transmitted to its peer,
  greatly increasing a server's endurance in communications-interrupted.
  This is supported using a new 'rewind state' record on the dhcpd.leases
  entry for each lease.
---

HTH

-Greg
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