Dynamic Host Configuration Protocol

The following dhcpd.conf file (compatible with ISOC DHCP 3) will give Grandstream (in this example) a different IP address from the rest of the network:
class "VoIP" {
       match if substring(hardware, 1, 2) = 00:0B;
}

authoritative;

subnet 192.168.0.0 netmask 255.255.0.0 {
max-lease-time 3600;
default-lease-time 1800;
option domain-name "yourdomain.name";
option subnet-mask 255.255.255.0;

pool {
 allow members of "VoIP";
 default-lease-time 500; # default lease 1 hour
 max-lease-time 500; # maximum lease 1 hour
 range 192.168.3.2 192.168.3.253;
}
pool {
 deny members of "VoIP";
 range 192.168.1.2 192.168.1.253;
}
}