dhcpd rewrite invalid client hostname for ddns

Question

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?

Hi @lenne! Did you ever figure out a solution? I have the same problem with my "iHome SmartPlug-967B65" device flooding my syslog with "dhcpd Unable to add forward map from iHome SmartPlug-967B65.myprivatedomain.com. to 10.100.111.47: REFUSED" (Note the space in the hostname.) — Jonathan Wheeler, Sep 20 '22 at 03:51

score -1 · Answer 1 · answered May 12 '19 at 13:03

-1

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.

answered May 12 '19 at 13:03

Uncleura

1

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

Vignesh SP · Answer 2 · 2018-01-24T16:06:19.007

-3

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: -

edited Jan 24 '18 at 16:06

answered Jan 24 '18 at 15:29

Vignesh SP

129
10

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 05 '18 at 19:59

dhcpd rewrite invalid client hostname for ddns

2 Answers2