[Dnsmasq-discuss] dnsmasq and external DHCPv6 servers

[Simon Kelley]

On 03/01/2022 21:55, Eric Dittman via Dnsmasq-discuss wrote:
> I have a Ubiquiti UDM SE.  It uses dnsmasq for DNS, DHCP, and RAs.  I
> have external DNS and DHCP servers so I want to send RA packets with
> the M and O flags set and the A flag reset, but I can't figure out the
> proper configuration to do that.  Right now just to get RA working on
> the subnets for IPv6 I have the following:
> 
> enable-ra
> ra-param=*,high,0
> domain=mydomain
> dhcp-range=2001:470:xxxx::,ra-names,slaac
> dhcp-range=2001:470:xxxx:10::,ra-names,slaac
> dhcp-range=2001:470:xxxx:20::,ra-names,slaac
> dhcp-range=2001:470:xxxx:40::,ra-names,slaac
> 
> I'm getting autoconf IPv6 addresses but I'm not seeing any DHCPv6
> packets on the external DHCPv6 servers (a pair per subnet).
> 
> Any ideas how I can get this working?

The dnsmasq RA code was designed to work with the dnsmasq DHCPv6 server,
so there's no direct support for this. I think the closest you can get
is to configure a static-addresses-only dhcp range

dhcp-range=2001:470:xxxx:10::,static,slaac

Which will not allocate any DHCPv6 leases, leaving the field open for
you other DHCPv6 servers, but will set the M and O bits.

Adding a new keyword to cover this circumstance is pretty straightforward.


Cheers,

Simon.