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Date: Thu, 31 Jan 2013 17:42:59 +0800
From: Kevin Lo <kevlo@kevlo.org>
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To: "Eggert, Lars" <lars@netapp.com>
Subject: Re: high cpu usage on natd / dhcpd
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On 2013/01/31 16:45, Eggert, Lars wrote:
> Hi,
>
>> I have a small system running FreeBSD 8.2 that does NAT using ipfw and
>> natd to systems attached to two interfaces: em0 and wlan0.  I have a
>> dhcpd daemon issuing leases on those interfaces.  The system has an em1
>> interface plugged into a cable modem where it obtains a DHCP lease from
>> an ISP.
>>
>> For some reason, when traffic from the Internet terminates on the system
>> itself (I scp a file from the computer) the natd and dhcpd processes
>> consume significant CPU, and the throughput is less than I expect.
>> Traffic that passes through to a computer behind the NAT flows without
>> causing the natd or dhcpd processes to measurably consume CPU.
> I see exactly the same issue on -STABLE. Have you been able to figure out the cause?

Use ipfw nat instead. It uses the libalias(3) in kernel and avoids
gigantic natd(8) overhead.

>
> Thanks,
> Lars
>

     Kevin