Automatic option 12 from DNS

[#1]

Our Infoblox service has several thousand hosts registered in Infoblox DNS+DHCP, all working well for several years. But the DHCP offers and request, although they return many DHCP options, for some reason don't include the hostname (DHCP option 12), even though it is configured in the host record.

What might we be missing to enable the DHCP replies automatically to include that hostname option?

[#2]

DHCP will only provide the requested options, in this scenario can you please validate that the client is asking for option12?

[#3]

Thanks for the reply.  Yes, I'll check that.  (I'm not a DHCP expert; does your reply suggest that option-12 must operate on an "only provide if requested" basis?)

Meanwhile, a bit more info, in case our problem lies elsewhere (e.g. not in DHCP or DHCP/option-12).

The overall problem is associated with installing RHEL7 clients using kickstart.  We have two domains, both supported by the Infoblox providing DHCP and DNS.  These domains ought to be equivalent, apart from reasoned, essential differences.   Hosts are generally single-connected, and are registered in the Infoblox with MAC+IP+name.  Across both, we want that RHEL7/kickstart process to get its hostname from the registration in the Infoblox.

In one domain any host being kickstart-installed receives its hostname, somehow, early in that kickstart process.  But in the second domain the host doesn't get the hostname.

If this is a "known issue" or FAQ (it doesn't seem to be) then pointers would be welcome.

A little more.  The main domain (where all works well) is (for example) "company.org".  The other domain (where this lack of hostname issue arises) is a subdomain, e.g. "sub.company.org".  One oddity I spotted, is that the DHCP/ACK returns the same "domain-name" option-15 "company.org" for both.  I wonder if that is precipitating a subsequent problematical behaviour in that "sub.company.org" context?