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I am trying to configure DHCP to use option 66 to provide a TFTP server to Sunray thin clients. The clients in a specific subnet must use a specific TFTP server so that they are served configuration specific to their subnet. Can I place the option in a subnet block as follows

 subnet netmask {

    # don't let clients modify their own A records
    ignore client-updates;

    # options
    option subnet-mask;
    option broadcast-address;

    option domain-name "";
    option domain-name-servers,;
    option routers;
    option 66 ip;

    option ntp-servers;
    option interface-mtu 1500;
    ddns-domainname "";
    ddns-rev-domainname "";
    pool {
            failover peer "dhcp-failover";


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up vote 2 down vote accepted

In isc-dhcp-server I create the option globally and then use it at the host level. You should be able to use vendor-option-space at the subnet level as well.

option space SunRay;
option SunRay.FWSrvr code 31 = ip-address;      
option SunRay.FWSrvr;
option SunRay.AuthSrvr code 21 = ip-address;
option SunRay.AuthSrvr;
option SunRay.AltAuth code 35 = array of ip-address;
option SunRay.AltAuth,;

host {
    vendor-option-space SunRay;
    hardware ethernet 00:ff:ff:ff:ff:ff;
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