Sudden Slow Performance

Tom Greaser tgreaser at
Mon Dec 15 15:09:59 UTC 2008

 Have you sniffed / snooped a station to see if its getting this Offer / ACK ?

>>> "Kelvin Williams" <kelvin-lists at> 12/15/08 9:52 AM >>> 
The entire network. 

-----Original Message-----
From: dhcp-users-bounces at
[mailto:dhcp-users-bounces at] On Behalf Of Tom Greaser
Sent: Monday, December 15, 2008 9:47 AM
To: 'Users of ISC DHCP'
Subject: RE: Sudden Slow Performance

Is this effecting All of your network or just a few subnets ?

 Ive had issues like this.. but only for specific networks.. I had a switch
would auto prune spanning tree .. Thus i would get the  DHCPDISCOVER  but
never the clients would never see the 

I manually made sure that network was never pruned..  

>>> "Kelvin Williams" <kelvin-lists at> 12/15/08 9:38 AM
Network good.  No errors on the interfaces.

No disk errors reported.

No patches applied.

CPU and Memory levels are good.

Number of clients always increases--but not a drastic amount.  Maybe 50 new

-----Original Message-----
From: dhcp-users-bounces at
[mailto:dhcp-users-bounces at] On Behalf Of Glenn Satchell
Sent: Monday, December 15, 2008 9:25 AM
To: dhcp-users at
Subject: Re: Sudden Slow Performance

>From: "Kelvin Williams" <kelvin-lists at>
>To: <dhcp-users at>
>Subject: Sudden Slow Performance
>Date: Mon, 15 Dec 2008 08:57:08 -0500
>X-Spam-Level: ***
>X-BeenThere: dhcp-users at
> We've been operating one of our DHCP Servers for approximately 6 months
> without any issues.  This server is on a network with about 2,500 hosts.
> The server has worked flawlessly until last week when it became extremely
> slow. 
> Clients are having to send multiple DISCOVERs before the server will
> respond, and sometimes the server does not respond timely to a REQUEST.
> Causing the clients to timeout and stop attempting.
> We've reviewed the server's load, and its very, very light.  vmstat
> show any bottlenecks in the processor or disk.  The current version we are
> running is 3.1.1; 
> As I stated, this all occurred within the last week.  Can anyone recommend
> something to check?  Or is there a way to get greater verbosity from the
> debug mode?
> Many thanks in advance.
> Kw

Have you checked out the hardware, network, etc? Maybe there is a hardware 
fault. Consider the slow dhcp response to be a symtim rather than the fault?

Could be a number of things:

- faulty network. try a different cable and/or switch port and/or nic

- disk errors. check logs for warnings or errors

- operating system patches. done any os patches around the time it went bad?

- any other system changes at that time?

- rogue process using all available cpu or memory?

- did the number of clients increase that week?


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