IP churn, maybe due to shared-network?

Jim Glassford jmglass at iup.edu
Wed Oct 31 18:01:49 UTC 2012

Hi Norman,

May not be related at all but for what it is worth if Cisco controller 
environment and might be related to other light weight controller 


"In the previous implementation, using the round robin algorithm was 
causing clients to obtain new IP addresses on every re-association, thus 
depleting IP addresses fast from the available DHCP pools. The new 
algorithm is based on the Client’s MAC address and operates in this way:..."


On 10/31/2012 9:18 AM, Norman Elton wrote:
> We've noticed that there is a higher-than-expected amount of IP churn
> for our wireless clients. That is, clients are connecting to the same
> network, but being assigned different IP addresses in the pool.
> I don't believe it's due to over-subscription. In the past few months,
> we've had a total of 13K unique devices with 12K available IP addresses.
> This might affect a transient device or two, but our long-term customers
> should retain the same IP.
> We do; however, have shared-networks setup. Each shared-network consists
> of a /21 (2000 clients) and a /23 (500 clients).
> So here's the question ... when there are two subnets defined inside a
> shared-network, does dhcpd always prefer using A, even if the client has
> an existing lease from B? That is, does it only use B if A is completely
> filled with active clients? This would certainly explain the behavior
> we're observing.
> Thanks!
> Norman Elton
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