[Dnsmasq-discuss] Can Dnsmasq be told not to advertise a specific prefix via RA?

Christopher Martin chrsmrtn at gmail.com
Sat Oct 27 18:17:29 BST 2018


Greetings,

Is it possible to prevent Dnsmasq from advertising a specific prefix via
router advertisements?

Here's my situation. My ISP provides a dynamic IPv6 prefix which, using
wide-dhcpv6, ends up assigned to interface bond0. Dnsmasq then advertises
the prefix on bond0 out to the LAN. The various hosts on the LAN use it,
together with IPv6 privacy extensions, to generate global IPv6 addresses.
So far so good.

For reference, my config is as follows:

dhcp-range=::,constructor:bond0,ra-only,infinite

Here's the problem. I also assign a ULA to bond0 (fd00:etc.). Dnsmasq also
advertises this prefix to the LAN, but I don't want it to, because then the
other hosts on the LAN end up generating addresses based on it, including
via IPv6 privacy extensions. Whereas what I want is to manually assign each
host its own specific, unchanging and easily remembered ULA, which should
also be the source IP used when connecting to various services around the
LAN. Too many ULAs cause problems.

Is there a way to instruct Dnsmasq to _not_ advertise the ULA prefix, but
to continue advertising the global prefix from my ISP? Perhaps this option
already exists and I've simply missed it - apologies if that's the case.

Thanks very much,

Christopher Martin
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