Number of interfaces limitation

Shane Kerr Shane_Kerr at isc.org
Wed Jul 19 11:04:35 UTC 2006


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Ivan V. Borodin wrote:
> Hello there,
> 
> Does anybody know something about total number of interfaces which dhcpd
> can listen? What about 2048 interfaces, for example?

As far as I know, there is no built-in hard limitation on the number of
interfaces which the ISC DHCP server can support.

However, the server uses the select() call to check for packets. This
function has a limited number of file descriptors it supports. In Linux,
for example, it only allows 1024. The DHCP server requires 2 file
descriptors per interface, plus a few extras for logging, writing
leases, and the like. So the practical limit is probably around 500
interfaces.

I'm curious what environment you have that needs more than a few interfaces!

- --
Shane
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