Re: Q: Max net dev and DHCP proxy?

Donald Becker (
Thu, 17 Jun 1999 15:22:34 -0400 (EDT)

On Thu, 17 Jun 1999, Roger Abrahamsson wrote:

> On Thu, 17 Jun 1999, Brad Dixon wrote:
> > 1) Is there a limit in the linux kernel or supporting network packages for
> > the number of network devices? I'm considering a project with up to 8
> Yep.. the limit is 8 ethernet devices.. however it is not too hard to
> increase it. I think the NET3-HOWTO does mention this...

Correction: there is no limit on the number of devices.

(Note: I'm ignoring ISA drivers for this discussion.)
There is a limit on the number of devices that you can pass options to.
That limit is 8 total devices for built-in drivers (eth0..eth7), and
typically the first eight devices for *each* driver loaded as a module.

So if you had 20 devices supported by the Tulip driver module (e.g. five
Znyx ZX346 quad-port boards), you could only override the transceiver type
and duplex of the first eight devices, but all 20 would be recognized.

If you had 16 ports as two quad-port Tulip boards (e.g. two ANA-6944A
boards) and two quad Starfire boards (the new Adaptec ANA-69044) you could
explicitly override the settings for all of the devices.

If this limit bothers you, it may be trivially increased at the top of each
driver -- it's documented. My assumption is that you have more than eight
interfaces, changing a constant is the least of the configuration issues.

Donald Becker
USRA-CESDIS, Center of Excellence in Space Data and Information Sciences.
Code 930.5, Goddard Space Flight Center, Greenbelt, MD. 20771

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