dhcp failover

Glenn Satchell Glenn.Satchell at uniq.com.au
Thu Jul 6 00:56:39 UTC 2006

There's two choices you can make here:

1) the dhcp server has a single interface and you use an ip-helper (or
relay agent) on each vlan,

2) the dhcp server has an interface on every vlan and you don't use
relay agents. This can work using a trunked interface that understands
vlan tagging and some magic on your switches, but means that every vlan
has to extend to where the dhcp server is. If you have far flung remote
vlan's then you probably don't want all the vlan broadcast traffic
being forwarded across your WANs.


>Date: Thu, 06 Jul 2006 10:11:40 +1000
>From: "John Abbott" <abbottj at stgeorge.com.au>
>To: <dhcp-users at isc.org>
>Subject: Re: dhcp failover
>we use dhcp helpers on each vlan has anyone got an opinion on this
>method? It seems to be working ok at present 
>>>> anthony <acqant at optonline.net> 07/06/06 4:17 AM >>>
>Tony Aldo wrote:
>> Hi, I have a 2 node cluster using the Linux HA project.
>> I am not using any of DHCP's built in failover features but instead
>> linux ha manage dhcp by keeping one node running dhcp at a time.
>> My question is, how bad is it not to mirror the leases databases
>between the
>> two servers?
>> Thanks
>> Tony
>Why are using HA?  If you have a cluster already running and just want
>to put dhcp on the two servers you can do that.  Just create two virtual
>ip's and put one real server in each vip pool.  Then run dhcp failover.
>Note:  This will only work if your forwarding dhcp requests using udp
>port 67.  I'm not sure how well it will work with broadcasts, if at all.
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