[Dnsmasq-discuss] DHCPv6 only

Simon Kelley simon at thekelleys.org.uk
Fri Apr 23 17:48:16 UTC 2021

On 21/04/2021 19:41, Aaron Oneal wrote:
> I am trying to configure my gateway running Dnsmasq to serve IPv6 addresses via SLAAC+RA and I don’t see how to enable that in a way that doesn’t also require IPv4 DHCP to be turned on.
> interface=br0
> dhcp-range=lan,::,constructor:br0,ra-stateless,64,600
> ra-param=br0,10,600
> enable-ra
> I already have a different server on the LAN that handles IPv4 DHCP so I don’t want Dnsmasq doing it.
> The problem is, Dnsmasq listens on IPv4 anyway and every time it receives an IPv4 DHCP message it spams my syslog with dozens of messages per second saying "no address range available for DHCP request via br0." I didn’t specify an IPv4 range because I don’t want one.
> I tried using `listen-address=<ipv6 addresses>` instead of `interface=br0` but then RA doesn’t seem to be active and my devices stop receiving IPv6 addresses.
> I can’t remove the IPv4 address from the interface because it’s a gateway.
> Is there a way to configure Dnsmasq for IPv6 only?

What you're doing should configure dnsmasq for IPv6 only, and a naive
attempt to reproduce you setup doesn't seem to have the same problem.
It's certainly not listening on IPv4 UDP port 68, which it would be if
serving DHCPv4.

Please could you let us know what version of dnsmasq you are running,
and what it logs at start-up? That would help to reproduce the bug at
this end.


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