Im using isc-dhcpd and bind9 to do ddns.

It is mostly working, but updates from clients with invalid names, like "leif_opo5" or "Danfoss Connect CC" are rejected.

I changed the hostname for my phone to leif-opo5, and it got registered, but I can't change the hardcoded hostname of the Danfoss unit.

I could hardcode the name and give it a fixed IP, but there might come other devices, so i wonder:

Is it possible for isc-dhcpd to rewrite hostnames with "bad characters", replacing with '-' for instance?


For each host with invalid hostname you can create "hostname" specification at it's own "host" declaration: .. # Color ink printer-scanner host EPSON1EE63C { hardware ethernet a4:ee:57:1e:e6:3c; hostname EpsonPrt; } .. Note EPSON1EE63C means nothing for dhcp daemon and for DDNS (if used). It means only original identifier for one of "host" declarations, but "hostname" instide block does.

  • Having to assign names manually defeats the idea of using DHCP to set the hostname. – Lenne May 13 '19 at 20:43

Can you try the below in DDNS section of the DHCP config?

ddns-updates on;
# DNS host name rewrite policy:
#   Name: Default
#   Valid characters: a-z0-9
#   Replace invalid characters by: -
  • Just like that? It looks like comments in plain text, not a valid config line – Lenne Jan 24 '18 at 19:24
  • Adding the lines as comments did nothing. Adding without # syntax error. – Lenne Feb 22 '18 at 22:15
  • Vignesh SP could you elaborate on your answer? – Lenne Mar 5 '18 at 19:59

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