DHCP + Bind integration

Philip Prindeville philipp_subx at redfish-solutions.com
Sat Dec 12 02:37:29 UTC 2020


Hi,

I’m the ISC-DHCP maintainer for OpenWRT.

I’m working on an out-of-the-box packaging for DHCP that allows it to update hostname and address assignments into DNS.

I’ve been following a couple of articles like:

https://www.talk-about-it.ca/setup-bind9-with-isc-dhcp-server-dynamic-host-registration/

https://docs.oracle.com/cd/E19469-01/820-6410-12/app_example_dns.html

But I’ve not been able to debug this or confirm that things are happening as they should.

I’ve gotten ISC DHCPD importing the rndc key without complaining, and can use that same key to apply commands like “rndc status” so that much seems to be working (in that the key seems to be accepted by named).

I see DHCPREQUEST and DHCPACK messages so it looks like hosts are getting leases, but when I query the name server locally for those same hosts it fails:

Dec 10 21:45:26 OpenWrt dhcpd: DHCPREQUEST for 192.168.2.4 from f4:0e:01:54:43:11 via eth0.2
Dec 10 21:45:26 OpenWrt dhcpd: DHCPACK on 192.168.2.4 to f4:0e:01:54:43:11 via eth0.2

But an “nslookup 192.168.2.4” fails, as does a lookup of the name I know this host is using.  “rndc sync” doesn’t show the zone files being updated on disk… they timestamps and file sizes don’t change.

Anyone have a canonical configuration that they know works properly with ISC-DHCP 4.4.1 and Bind 9.16.8?  Or at least steps to troubleshoot the configuration?

OpenWRT is handy in home networks, but I’m trying to get it to work in a small business environment where you have laptops, printers, tablets, etc. you want registering themselves in an Intranet/split-horizon DNS configuration.

Was also wondering if there was an easy way to prime the DNS for hosts with static assignments (that hence don’t have host { } records in dhcpd.conf and are outside of the subnet “range” statement)?

Thanks,

-Philip



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