Question on pick-first-value and valid FQDN

Jim Glassford jmglass at
Fri Oct 12 15:09:13 UTC 2012


Running DHCP Server 4.1.1-P1 and had a question on pick-first-value with 
dynamic dns updates. All working great doing ddns, using the ethernet 
address for wireless and student machines FQDN.

subnet netmask {
  option routers;
   pool {
   default-lease-time 3600; max-lease-time 3600;
   ignore client-updates;
   ddns-updates on;
   ddns-rev-domainname "";
   ddns-hostname =  binary-to-ascii (16, 8, "-",substring (hardware, 1, 6));
   ddns-domainname "";

Starting a VMware VDI scope and want to start creating the FQDN with the 
host name supplied by the VM clients. Considering the following, if host 
name supplied, use it, if not create one using the ethernet address. 
Same as above, just changed the ddns-hostname line to:

ddns-hostname = pick-first-value ((option host-name), (binary-to-ascii 
(16, 8, "-",substring (hardware, 1, 6))));

If invalid host name supplied, underscore, slash, etc, should I do more 
conditional evaluation of the supplied name or would an invalid supplied 
host name fail the evaluation, be considered a null value then move to 
the second choice?


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