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Date:      Wed, 25 Sep 2002 11:07:17 -0300
From:      "Cody Swanson" <cswanson@pei.eastlink.ca>
To:        <freebsd-hackers@freebsd.org>
Subject:   Problems with NATd performance...
Message-ID:  <005a01c2649c$dba0f5f0$0401a8c0@win2000>

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Hello all,

I just setup a 4.6.2 machine locally on my network at home to replace an
aging Linux NAT box I had going. Clients behind the new box can only get
100k/sec downloads while clients behind the old Linux box (running ipchains)
get 400k/sec+ downloads off the same cable modem. Locally on the new FreeBSD
box I can get 400k/sec downloads with lynx, it just seems as if the NAT is
not framing packets right. Also, I have tried downloads from other freeBSD
machines, Linux machines and windows2000 machines from inside the network.
All max out at around 100k/sec on a download. Again, if I download on the
box it self I can see 400k/sec.

The machine is a PIII500 with 512mb ram. I have a 3com 3c905 nic for the
internal LAN and a D-Link 530TX revA card for the external link to my cable
modem. I rebuilt the GENERIC kernel with the following options:

options         IPFIREWALL
options         IPDIVERT

And I added the following lines to rc.conf (as noted in the handbook)

gateway_enable="YES"
kern_securelevel_enable="NO"
ifconfig_xl0="inet 192.168.1.254  netmask 255.255.255.0"
ifconfig_vr0="DHCP"
firewall_enable="YES"
firewall_type="OPEN"
natd_enable="YES"
natd_interface="vr0"
natd_flags=""

Also, here is a copy of an ifconfig of the internal interface:

pinky# ifconfig -xl0

  xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        inet 192.168.1.254 netmask 0xffffff00 broadcast 192.168.1.255
        inet6 fe80::260:97ff:fed5:5601%xl0 prefixlen 64 scopeid 0x2
        ether 00:60:97:d5:56:01
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active

At first I thought this was a windows TCP window size issue, but then when
my freebsd and Linux boxes showed similar results I concluded it's an issue
with my Nat config. Is there anything I can do to increase the throughput? I
heard that 3com 3c905's are not the best card going but I have crappy Dlink
DE220's in my old gateway and they did far more throughput through an old
486DX4.  Any help would be greatly appreciated.




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