DHCP transactions per second

[Glenn Satchell]

>Date: Mon, 18 Jun 2007 09:35:56 +0100
>To: dhcp-users at isc.org
>From: Simon Hobson <dhcp1 at thehobsons.co.uk>
>Subject: Re: DHCP transactions per second
>
>Ian Anderson wrote:
>>With further investigation it appears that we are getting multiple
>>requests for each client.  We have several ip helper  addresses (foundry
>>switchs) in our network, and I believe we may have a misconfiguration
>>somewhere.
>>
>>For example, if a client has never powered up on our network before it
>>performs the typical DISCOVER/OFFER/REQUEST/ACK  Because all of those
>>are broadcast the dhcp server is receiving the client messages 4 times. 
>>(and responding 4 times as well) 4 DISCOVERS / 4 REQUESTS.  I know dhcp
>>can cope with this, and the server will ACK the first REQUEST it
>>receives from any given client.   Even though dhcp can handle this, is
>>this a significant source of additional load on the server?
>
>More or less, each request adds one unit of extra work.
>
>>Are duplicate broadcasts treated any differently by dhcp than receiving just
>>one broadcast?
>
>No
>
>>Or in other words, does dhcp know the difference between a normal 
>>broadcast and one that is a duplicate?
>
>How can it ? They are simply relayed packets and will be identical 
>other than the GIAddr - there is nothing to say "this is a duplicate".
>
>>I would imagine in order to get an accurate representation of your dhcp
>>servers transactions per second you would need to fix whatever is
>>causing the duplicate messages.

In terms of redundancy having more than one relay agent could be
considered "good practice". Perhaps reconfiguring your relay agents so
that between your multiple foundry devices you have only two for each
subnet.

regards,
-glenn