I've been trying to get mac addresses with a certain OUI into a certain address pool. I haven't been able to get it to work at all. Here is a snippet of my dhcpd.conf and how it's applied.

class "testphones" {
        match hardware;
subclass "testphones" 1:00:07:3b:cb:c9:cf; 

class "avaya-9630" {
   match if substring(hardware,1,3) = "00:07:3b"; 

subnet netmask {
    option subnet-mask;
    option broadcast-address;
    option routers;
    option avaya-242 "OPTIONS"

    pool {
        deny members of "testphones";
        deny members of "avaya-9630";


subnet 10.X.128.0 netmask {
    option subnet-mask;
    option broadcast-address 10.X.135.255;
    option routers  10.X.128.5;
    option avaya-242 "OPTIONS";
    pool {
            range  10.X.129.1  10.X.134.255;
            allow members of "testphones";
            allow members of "avaya-9630";

I don't get any of the mac addresses to match the "avaya-9630" class. They all get handed IPs from the first ( subnet. The "testphone" does work, though. It goes into the 10.X subnet.

Why does the "testphone" class work but not the "avaya-9630" class?

One thing that might cause a problem is I'm using a petty old version of ISC DHCP (3.0.1). I don't know if the syntax is different for that older version. The man pages seem to indicate I'm doing it right.

I've tried various iterations of the "match" line. I tested with the following:

match if substring(hardware,1,3) = "1:00:07:3b";
match if substring(hardware,0,3) = "1:00:07:3b";
match if substring(hardware,1,4) = "1:00:07:3b";

None worked.

Your thoughts are appreciated.

1 Answer 1


It works without the quotation mark. For example, in this case:

match if substring(hardware,1,3) = 00:07:3b;

This way, it works in my production environment.

  • 4
    Please give a working example of what you mean.
    – Sven
    Apr 12, 2018 at 11:37
  • Sure. Example added.
    – Zsombor
    Apr 13, 2018 at 18:11

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