Lease File of RAM Disk
Waqas Asghar
waqas.asghar at aol.com
Thu May 15 12:35:04 UTC 2014
Lease File of RAM Disk
Hi
Well I have a script in place which copies the lease file every five minutes to my harddisk.
I believe the option of starting the server again with an empty lease file should work since it should get the file populated from the backup server once it starts,however I just wanted to confirm my understanding of the process in which the primary & backup servers share lease files before I go for the reboot.
Regards,
Waqas Asghar
+923335495619
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Today's Topics:
1. Re: DHCPERF & ISC DHCP (Waqas Asghar)
2. Lease File of RAM Disk (Waqas Asghar)
3. Re: Lease File of RAM Disk (Simon Hobson)
4. Re: Lease File of RAM Disk (A.L.M.Buxey at lboro.ac.uk)
5. Re: Lease File of RAM Disk (Simon Hobson)
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Message: 1
Date: Thu, 15 May 2014 01:42:35 -0400 (EDT)
From: Waqas Asghar <waqas.asghar at aol.com>
To: dhcp-users at lists.isc.org
Subject: Re: DHCPERF & ISC DHCP
Message-ID: <8D13E179B61E3C8-678-11023 at webmail-d222.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"
Yes that was a type sorry for that.
Regards,
Waqas Asghar
+923335495619
-----Original Message-----
From: dhcp-users-request <dhcp-users-request at lists.isc.org>
To: dhcp-users <dhcp-users at lists.isc.org>
Sent: Thu, May 15, 2014 2:37 am
Subject: dhcp-users Digest, Vol 67, Issue 10
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Today's Topics:
1. DHCPERF & ISC DHCP (Waqas Asghar)
2. Re: DHCPERF & ISC DHCP (Simon Hobson)
3. OMAPI ip-address lookup always fail (dan le bray)
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Message: 1
Date: Tue, 13 May 2014 14:45:49 -0400 (EDT)
From: Waqas Asghar <waqas.asghar at aol.com>
To: dhcp-users at lists.isc.org
Subject: DHCPERF & ISC DHCP
Message-ID: <8D13CF2B196A0C3-298C-3710 at webmail-vm031.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"
Hi
I have configured the latest version of ISC DHCP on a centos server and trying
to test it using dhcperf installed on another server.
I am using simple syntax for dhcperf in which I send a single dhcp discover to
the DHCP using the following syntax
./dhcperf --server 192.168.14.67 --discover
But I get no free leases message from my DHCP server.My DHCP is hosted on
192.168.14.66.
Furthermore I tried sending the DHCP request from a laptop and it worked fine
and got the IP.
Can someone plz guide as to what will be the correct syntax in this case.
Regards,
Waqas Asghar
+923335495619
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Message: 2
Date: Tue, 13 May 2014 22:04:16 +0100
From: Simon Hobson <dhcp1 at thehobsons.co.uk>
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: Re: DHCPERF & ISC DHCP
Message-ID: <C879C22A-11C4-437B-BEEC-78A5BA12B7FA at thehobsons.co.uk>
Content-Type: text/plain; charset=us-ascii
Waqas Asghar <waqas.asghar at aol.com> wrote:
> ./dhcperf --server 192.168.14.67 --discover
>
> But I get no free leases message from my DHCP server.My DHCP is hosted on
192.168.14.66.
Is that a typo, or are you trying to get a lease from the wrong address ?
------------------------------
Message: 3
Date: Wed, 14 May 2014 10:18:13 +0200
From: dan le bray <dlb at univ-lehavre.fr>
To: dhcp-users at lists.isc.org
Subject: OMAPI ip-address lookup always fail
Message-ID: <537326C5.5030304 at univ-lehavre.fr>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hello,
when trying to lookup a lease using an ip-address (as mentionned in the
omshell man page), the operation fails with the 'can't open object: not
found' error message. It does work well when looking up a host object
using either a 'name' or 'hardware address' atribute but always fail
when using the ip-address attribute of a lease object. The result is the
same whether the lease was created using OMAPI or defined in the dhcpd.conf.
I searched this list but didn't find any clue about this.
We're using ISC DCPd 4.2.2/x86_64 on Debian Wheezy (7.5).
Example#1: hardware address lookup:
> new host
obj: host
> set hardware-address = 00:50:56:aa:bb:ff
obj: host
hardware-address = 00:50:56:aa:bb:ff
> open
obj: host
hardware-address = 00:50:56:aa:bb:ff
ip-address = 0a:64:0a:64
name = "bidon"
hardware-type = 00:00:00:01
Example#2: name lookup:
> new host
obj: host
> set name = "bidon"
obj: host
name = "bidon"
> open
obj: host
name = "bidon"
ip-address = 0a:64:0a:64
hardware-address = 00:50:56:aa:bb:ff
hardware-type = 00:00:00:01
Example#3: ip address lookup:
> new lease
obj: lease
> set ip-address = 10.100.10.100
obj: lease
ip-address = 0a:64:0a:64
> open
can't open object: not found
obj: lease
ip-address = 0a:64:0a:64
Any help would be helpful.
--
Daniel Le Bray - CRI / P?le Systeme et Reseaux
Universite du Havre - 25 rue Philippe Lebon - 76600 Le Havre
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Message: 2
Date: Thu, 15 May 2014 01:50:45 -0400 (EDT)
From: Waqas Asghar <waqas.asghar at aol.com>
To: dhcp-users at lists.isc.org
Subject: Lease File of RAM Disk
Message-ID: <8D13E18BF57A40F-678-110B2 at webmail-d222.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"
Hi
I am running Internet Systems Consortium DHCP Server 4.2.1-P1 on a solaris
platform in active/backup config.
The ram usage on my primary server is increasing and during the time of log
rotation free RAM comes down to 400MB's.To fix that I plan on rebooting my
primary server.
The lease file on my servers are placed on a RAM DISK,now when I will be
rebooting the server the RAM disk will be lost & I would have to recreate it.
What should I do for the lease file in this case should I take a backup of the
lease file and place it on the new ramdisk and start the server or should I
start the server with an empty lease file.
Regards,
Waqas Asghar
+923335495619
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Message: 3
Date: Thu, 15 May 2014 08:00:42 +0100
From: Simon Hobson <dhcp1 at thehobsons.co.uk>
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: Re: Lease File of RAM Disk
Message-ID: <DE4C39CB-0473-4962-8A02-A92A325DFC07 at thehobsons.co.uk>
Content-Type: text/plain; charset=us-ascii
Waqas Asghar <waqas.asghar at aol.com> wrote:
> The lease file on my servers are placed on a RAM DISK,now when I will be
rebooting the server the RAM disk will be lost & I would have to recreate it.
>
> What should I do for the lease file in this case should I take a backup of the
lease file and place it on the new ramdisk and start the server or should I
start the server with an empty lease file.
You should do neither of those - you should put your leases file on persistent
storage. If you don't then sooner or later you *WILL* lose your leases file and
that will cause you a truckload of problems as your DHCP servers will no longer
know what has already been leased to which client.
However, when you say you have an "active/backup" setup, what do you mean as
that is not something the ISC server supports out of the box. If you have a
failover config, then I believe (but I'm not an expert and I don't use failover
myself) you should be able to reboot one server, create a new empty leases file,
and then that server will pull the leases from the partner. That only works if
you never, ever, for any reason, restart both servers at the same time*.
* Where "same time" means any period shorter than the time it takes for one
server to reboot and transfer the leases file from it's partner. Dunno about
you, but even with reliable mains power and investment in UPS etc, we've still
had "inconvenient events" at work :-(
------------------------------
Message: 4
Date: Thu, 15 May 2014 08:11:30 +0000
From: A.L.M.Buxey at lboro.ac.uk
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: Re: Lease File of RAM Disk
Message-ID: <20140515081130.GB30922 at lboro.ac.uk>
Content-Type: text/plain; charset=us-ascii
Hi,
> You should do neither of those - you should put your leases file on persistent
storage. If you don't then sooner or later you *WILL* lose your leases file and
that will cause you a truckload of problems as your DHCP servers will no longer
know what has already been leased to which client.
have a process to copy the lease file to persistant storage - and have a system
startup
script to copy it to ramdisk. have such things in your DHCP sysV or systemd
scripts so
restart of service will store/copy and recover too.
if you're only doing linked/static leases or you really take the 'dynamic' part
to heart
then losing all lease info isnt a problem - well, it is if your DHCP server isnt
checking
leases are in use before handing addresses out :-)
alan
------------------------------
Message: 5
Date: Thu, 15 May 2014 09:44:04 +0100
From: Simon Hobson <dhcp1 at thehobsons.co.uk>
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: Re: Lease File of RAM Disk
Message-ID: <70DC7C43-F6E3-481C-9ABE-46A5FEE4D8BF at thehobsons.co.uk>
Content-Type: text/plain; charset=us-ascii
A.L.M.Buxey at lboro.ac.uk wrote:
> have a process to copy the lease file to persistant storage - and have a
system startup
> script to copy it to ramdisk.
Well as long as it copies the file periodically, not just on a server/process
shutdown, then that will significantly reduce the problem. Just copying the file
on shutdown is a bad idea - it won't get copied on power failure or server
crash.
> if you're only doing linked/static leases or you really take the 'dynamic'
part to heart
> then losing all lease info isnt a problem - well, it is if your DHCP server
isnt checking
> leases are in use before handing addresses out :-)
Actually, it's a big problem.
The server will start up with a blank sheet. It will start offering out leases
that are already leased out - what happens next varies according to the
particular combination of circumstances :
1) The device with that address isn't online at the time. A new device gets the
address, you now have the address leased to two clients - and are dependent on
the original one recognising this and "doing the right thing" when it comes back
online.
2) The device with that address is online, but the server doesn't detect it -
ping before offer is "less useful" now that so many systems default to not
responding to pings. The device offered the lease now has to decline it - but
the server will keep offering it. At the very least you'll fill your logs with
DHCP Decline messages.
3) The server detects the address is in use - and marks it as abandoned. It will
now no longer offer it except when it runs out of other candidates. It will in
effect run with a much smaller pool which increases client address churn.
Of course, if having a network that "just works" and is fairly stable isn't a
priority for you then these are not problems.
If only static leases - no it's not a problem, but then your leases file will be
empty anyway.
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