dnsmasq tags and conditional dns server

ok, i fixed it (wrt my particular request) and i'll post what i've got here in case it helps someone else.

so my requirement was handing out different dns server (and perhaps different gw) to different hosts, and this seems to work:

dhcp-range=set:green,192.168.1.80,192.168.1.150,infinite

# red network
dhcp-host=11:22:33:44:55:66,hosta,192.168.1.11,infinite,set:red
dhcp-host=66:55:44:33:22:11,aa:bb:cc:dd:ee:ff,hostb,192.168.1.12,infinite,set:red

# green network mobile
dhcp-host=dd:dd:dd:dd:dd:dd,android1,192.168.1.21,infinite,set:green
dhcp-host=cc:cc:cc:cc:cc:cc,android2,192.168.1.22,infinite,set:green

unless expicility set otherwise, everything is tagged green. Some certain MACs are tagged red. Then to do the different dns server and different gw you can do:

# options
dhcp-option=tag:green,option:dns-server,192.168.1.1,192.231.a.b   # ,8.8.8.8,8.8.4.4
dhcp-option=tag:red,option:dns-server,192.168.1.c
dhcp-option=tag:green,option:router,192.168.1.1
dhcp-option=tag:red,option:router,192.168.1.c

some other notes / context that i found helpful about this, and also about the net / set / tag options:

  • The optional set: sets an alphanumeric label which marks this network so that dhcp options may be specified on a per-network basis. When it is prefixed with 'tag:' instead, then its meaning changes from setting a tag to matching it. Only one tag may be set, but more than one tag may be matched.
  • More than one tag can be set in a dhcp-host directive (but not in other places where "set:" is allowed)
  • This system evolved from an earlier, more limited one and for backward compatibility "net:" may be used instead of "tag:" and "set:" may be omitted. (Except in dhcp-host, where "net:" may be used instead of "set:".) For the same reason, '#' may be used instead of '!' to indicate NOT.

therefore i think it's safe to just:

  • use set and tag, and avoid using net (since it's the old way)
  • use set in your dhcp-range and dhcp-host, to assign the tags, and
  • use tag in your options to match the tags that you've already set.
  • as an aside on of those dhcp-hosts you can see with multiple mac addresses, because it's the eth0 and wlan mac's for the same box.

seems to work for me anyway, perhaps this will help someone.

Tags:

Dns

Dnsmasq

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