<html><head><title>Re: Partner Down State</title>
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<td><span style=" font-family:'arial'; font-size: 9pt;">Hi Greg <br>
<br>
Thanks for your reply.<br>
<br>
I am operating "Internet Systems Consortium DHCP Server 4.2.1-P1".<br>
<br>
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" ?<br>
<br>
<b>Regards, <br>
Waqas Asghar<br>
<br>
<br>
</b><span style=" font-size: 10pt;">-----Original Message-----<br>
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Today's Topics:<br>
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1. Partner Down State (Waqas Asghar)<br>
2. Re: Partner Down State (Gregory Sloop)<br>
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----------------------------------------------------------------------<br>
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Message: 1<br>
Date: Fri, 28 Nov 2014 02:36:36 -0500<br>
From: Waqas Asghar <</span><a style=" font-family:'courier new'; font-size: 9pt;" href="mailto:waqas.asghar@aol.com">waqas.asghar@aol.com</a><span style=" font-family:'courier new'; font-size: 9pt;">><br>
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Subject: Partner Down State<br>
Message-ID: <</span><a style=" font-family:'courier new'; font-size: 9pt;" href="mailto:8D1D8F52CC643F5-7B8-28932@webmail-vd010.sysops.aol.com">8D1D8F52CC643F5-7B8-28932@webmail-vd010.sysops.aol.com</a><span style=" font-family:'courier new'; font-size: 9pt;">><br>
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<br>
Hi<br>
<br>
<br>
I am operating two ISC DHCP servers as active/backup.<br>
However during an outage I would like to operate the backup server in "partner <br>
down" state so that it can utilize all the IP's.Any suggestion how can I <br>
manually place the backup server in partner down state.I have checked there is a <br>
script that can be used but that's not working for me will appreciate it someone <br>
can help me out here.<br>
<br>
<br>
<br>
Regards,<br>
Waqas Asghar<br>
<br>
<br>
<br>
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Message: 2<br>
Date: Thu, 27 Nov 2014 23:46:54 -0800<br>
From: Gregory Sloop <</span><a style=" font-family:'courier new'; font-size: 9pt;" href="mailto:gregs@sloop.net">gregs@sloop.net</a><span style=" font-family:'courier new'; font-size: 9pt;">><br>
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Subject: Re: Partner Down State<br>
Message-ID: <</span><a style=" font-family:'courier new'; font-size: 9pt;" href="mailto:1386419988.20141127234654@sloop.net">1386419988.20141127234654@sloop.net</a><span style=" font-family:'courier new'; font-size: 9pt;">><br>
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<br>
<br>
Hi <br>
<br>
I am operating two ISC DHCP servers as active/backup.<br>
However during an outage I would like to operate the backup server in "partner <br>
down" state so that it can utilize all the IP's.Any suggestion how can I <br>
manually place the backup server in partner down state.I have checked there is a <br>
script that can be used but that's not working for me will appreciate it someone <br>
can help me out here.<br>
<br>
<br>
Regards, <br>
Waqas Asghar<br>
<br>
<br>
There's a new option in, IIRC, 4.2.0+ "auto partner down" that should do what <br>
you want.<br>
However, be *very* careful with it. There are reasons that the partners might <br>
not be able to reach each other, and thus not really be down - and both servers <br>
will then assume they have the whole IP block to lease from and will be issuing <br>
duplicate leases all over the place. As you can imagine, this would be a very <br>
bad(tm) situation. So, use it carefully and consider things carefully.<br>
<br>
There's also another option that is also in 4.2.0+ that will allow the remaining <br>
partner to "rewind" leases issued by the partner and "re-lease" them - thus <br>
giving the remaining partner a lot more endurance. It's also a lot safer than <br>
the "auto partner down" directive. <br>
<br>
From the release notes for 4.2.0a1<br>
---<br>
- An optimization described in the failover protocol draft is now included,<br>
which permits a DHCP server operating in communications-interrupted state<br>
to 'rewind' a lease to the state most recently transmitted to its peer,<br>
greatly increasing a server's endurance in communications-interrupted.<br>
This is supported using a new 'rewind state' record on the dhcpd.leases<br>
entry for each lease.<br>
---<br>
<br>
HTH<br>
<br>
-Greg<br>
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<span style=" font-family:'Courier New'; font-size: 9pt;">Best I can say, is read the docs.<br>
<br>
See here:<br>
https://kb.isc.org/article/AA-00333 <br>
<br>
...and the man page.<br>
<br>
---<br>
This is from a search on the web from the man page for ISC's dhcp server.<br>
<br>
---<br>
The auto-partner-down statement<br>
<br>
auto-partner-down seconds;<br>
<br>
This statement instructs the server to initiate a timed delay upon<br>
entering the communications-interrupted state (any situation of being<br>
out-of-contact with the remote failover peer). At the conclusion of<br>
the timer, the server will automatically enter the partner-down<br>
state. This permits the server to allocate leases from the partner's<br>
free lease pool after an STOS+MCLT timer expires, which can be dan-<br>
gerous if the partner is in fact operating at the time (the two<br>
servers will give conflicting bindings).<br>
<br>
Think very carefully before enabling this feature. The partner-down<br>
and communications-interrupted states are intentionally segregated<br>
because there do exist situations where a failover server can fail to<br>
communicate with its peer, but still has the ability to receive and<br>
reply to requests from DHCP clients. In general, this feature should<br>
only be used in those deployments where the failover servers are<br>
directly connected to one another, such as by a dedicated hardwired<br>
link ("a heartbeat cable").<br>
<br>
A zero value disables the auto-partner-down feature (also the<br>
default), and any positive value indicates the time in seconds to<br>
wait before automatically entering partner-down.<br>
---<br>
<br>
But really, I think you can dig from there - "man dhcpd" from a command prompt should not be too taxing, IMO.<br>
<br>
If you know enough to setup a fail-over partner, you really should know enough to give a look at the man page, or even do a few google searches. [It's frustrating to feel like you're asking me to regurgitate a man page, or generate a full config file for you, when, as far as I can tell, you've not even attempted the same. If you'd tried and were unable to get it working, perhaps I'd feel different - though how you could fail in simply inserting something like "auto-partner-down 60" in your config, for example, is beyond me.]<br>
<br>
Also, as I re-read your initial post; a follow-up. You can use OMAPI to put the remaining server in partner down mode, manually. <br>
Here's a start: </span><a style=" font-family:'Courier New'; font-size: 9pt;" href="https://www.google.com/search?q=dhcpd+omapi+partner+down+mode&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb">https://www.google.com/search?q=dhcpd+omapi+partner+down+mode</a><br>
<br>
<span style=" font-family:'Courier New'; font-size: 9pt;">[However, the options I outlined may be more suitable. Inevitably, when one of the partners goes down, you'll be far from somewhere you can manually put one in partner-down mode and things will start to go wrong - so look at the docs and see what makes the most sense for your application.]<br>
<br>
Lastly, I'm not sure what platform you're on, but it seems to me that something newer than 4.2.1 might be advisable. [But perhaps that's what supported by your distro.]<br>
<br>
-Greg<br>
<br>
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