How many fixed address ?

David W. Hankins David_Hankins at
Fri Sep 8 18:16:59 UTC 2006

On Fri, Sep 08, 2006 at 03:03:03PM +0200, Anders R Gustavsson wrote:
> Hi,
> I am going to implement a dhcp server with a large number of clients. 
> Maybe up to 5-6000.
> That I want to do is to use fixed addresses to mac. Like below...
> host cd-i3m0010 {hardware ethernet 00:02:61:03:78:0a;fixed-address 
>;}# M110K443R2A0-0000163674
> host cd-i3m0011 {hardware ethernet 00:02:61:03:77:4a;fixed-address 
>;}# M110K443R2A0-0000163605
> host cd-i3m0012 {hardware ethernet 00:02:61:03:77:d4;fixed-address 
>;}# M110K443R2A0-0000163708
> How many static mac-entries can I use with isc dhcpd server v3 ?

As many as you want.

The host records go into a hash table that has 9973 buckets (there
are separate hash tables for mac addresses and client identifiers).

The hash algorithm used is probably not the least collision
prone for mac addresses, so you'll probably get multiple
records in one bucket at ~6000, but probably not many.

It's hard to say without instrumenting the hash tables to dump

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