[Dnsmasq-discuss] DHCPv6 only

Aaron Oneal aaron at spicypixel.com
Sat Apr 24 03:28:36 UTC 2021

Geert, thank you that is a creative solution. I wasn’t able to determine how to configure that so I determined a way to change my network topology instead to work around.

Simon, thank you for your assistance. Let me see if I can help track this down.

Dnsmasq is listening on 67:
udp        0      0                                *                                                       PID/dnsmasq

Nothing logged on startup in syslog other than:
Apr 23 20:13:14 dnsmasq-dhcp[PID]: no address range available for DHCP request via br0

ASUS router with this firmware:

Dnsmasq version:
Dnsmasq version 2.84-42-g433dc70  Copyright (c) 2000-2021 Simon Kelley
Compile time options: IPv6 GNU-getopt no-RTC no-DBus no-UBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset no-auth cryptohash DNSSEC no-ID loop-detect no-inotify no-dumpfile

Line generating the error (rfc2131.c Line 345):

> On Apr 23, 2021, at 10:48 AM, Simon Kelley <simon at thekelleys.org.uk> wrote:
> 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.
> Simon.

> On Apr 21, 2021, at 1:09 PM, Geert Stappers via Dnsmasq-discuss <dnsmasq-discuss at lists.thekelleys.org.uk> wrote:
> Path I would go is configuring dnsmasq to only IPv4 DHCP reply to known
> MAC-addresses. And than have a MAC address configured that none of the
> clients has.  No, I never have travelled that path. I do like to known
> if it lead to the wanted goal.
> Groeten
> Geert Stappers

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