North American Network Operators Group

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RE: cpu needed to NAT 45mbs

  • From: David Schwartz
  • Date: Thu Nov 08 18:01:02 2007

> From my experience, a fast P4 linux box with 2 good NICs can NAT
> 45Mbps easily.  I am NAT/PATing >4,000 desktops with extensive
> access control lists and no speed issues.  This isn't over a 45Mb
> T3--this is over 100 Mb Ethernet.
> --Patrick Darden
> --ARMC, Internetworking Manager

	A second CPU or core will help tremendously. We used to use single-CPU
boxes for this and we noticed that traffic sometimes stalls when the machine
has to do some task other than NATting, such as expiring idle flows. Having
a second CPU or core will help keep latency much more uniform.

	We have a few dual 3.2Ghz Xeon boxes (not the ones based on Core, the older
ones) that NAT/FW across two GE interfaces. They do quite well up to about
300Mb/s, then we start to see issues. We believe the issues are due to
overloading the NB-SB link. A more modern mobo probably wouldn't have this