[CentOS] Performance of CentOS as a NAT gateway

[Bart Schaefer]

On 9/9/07, Barry Brimer <lists at brimer.org> wrote:
> Maybe it is time for some kernel networking tuning.

After doing a bit of research:

http://www.acc.umu.se/~maswan/linux-netperf.txt
http://wwwx.cs.unc.edu/~sparkst/howto/network_tuning.php
http://proj.sunet.se/E2E/tcptune.html
http://www.linuxguruz.com/iptables/howto/2.4routing-13.html
http://www-didc.lbl.gov/TCP-tuning/linux.html

I ended up with this:

net.core.rmem_default = 873800
net.core.wmem_default = 655360
net.core.rmem_max = 8738000
net.core.wmem_max = 6553600
net.ipv4.tcp_rmem = 8192 873800 8738000
net.ipv4.tcp_wmem = 4096 655360 6553600
net.ipv4.tcp_mem = 195584 873800 8738000

(The first number in tcp_mem is the original default.)

Plus:

ifconfig eth0 txqueuelen 1000
ifconfig eth1 txqueuelen 1000

Unfortunately so far this doesn't seem to have made any difference.
We've had a load peak going since early this morning and the traffic
looks exactly like it did last week.