Watching performance on a DHCP Server

Simon Hobson dhcp1 at
Sun Apr 27 06:41:45 UTC 2008

Anders Rosendal wrote:

>The biggest problems with intensive DHCP-storms due to network 
>outages longer then leasetime is that if the server, or cluster of 
>servers is not quick enough to provide answers is that the request 
>made by the clients times out before the client receives a answer 
>from the server. This causes the server to only answer requests that 
>are "old" and no clients receives there addresses. The solution to 
>implement when stuck in this situation is to block requests in the 
>routers for large part of the network, and then bit by bit opening 
>up everything again. On the company which I work we have an inhouse 
>built DHCP-server which is quite powerful, we have ~550000 leased 
>IP's in the system. Althoug when we have had long outages we have 
>been forced to used the solution described above. You should monitor 
>the udp-in-queue on the server / servers, checking that the server 
>manages to answer clients quickly enough.

Does this mean that a smaller udp queue would be better ? Ie, throw 
away excess requests (the client will try again soon) rather than 
allow them to get stale ?

Or in some situations, rate limiting DHCP packets in the routers ?

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