[Dnsmasq-discuss] IPv6: Router with RA + static DHCPv6 from dnsmasq on separate host

[M. Buecher]

On 2017-08-18 15:38, M. Buecher wrote:
> Hello dnsmasq fellows,
> Hello Simon,
> 
> I want to assign additional static DHCPv6 global unicast addresses 
> (GUA) to some machines (mainly servers).
> Yet I have failed to do so with dnsmasq.

Got it working. Indeed it was working.

> The GUA prefix [1] is advertised by my router "AVM FRITZ!Box 7490" [3].
> Its Router Advertisement (RA) has M-, O- and A-flag set. Priority is 
> middle.
> And it is the standard gateway for Internet connections.
> 
> dnsmasq 2.76 is running on a Raspberry with Raspbian 8 "Jessie" [4].
> It is the only DNSv4/v6 server in the LAN and serves the local domain.
> All other requests are forwarded by dnsmasq via IPv4 to the DNS relay 
> of the router, this way those requests are resolved by the ISP's DNS 
> servers.
> It also advertises the Unique Local Addresses (ULA) [2] for the LAN via 
> RA and assigns addresses via DHCPv6 only.
> The host with dnsmasq (Raspberry) has a GUA via SLAAC by the router's 
> RA.
> 
> Test machine is Windows 10 with latest updates.
> It got its ULA via DHCPv6 from dnsmasq and has a GUA via SLAAC by the 
> router's RA.
> Additionally a second GUA is present due to Windows' IPv6 privacy 
> extensions for outgoing connections.
> *But* it doesn't have it's static GUA from dnsmasq!
> 
> Am I missing something in my dnsmasq configuration (see below)?
> Or do I have to configure the clients in another way?
> Any other enhancements for my configuration?

If you run "ipconfig /renew6 <interface>" on Windows (here 10), then 
Windows only requests the existing IPv6 addresses to be renewed.
To also get new addresses for the Windows you have to release all IPv6 
addresses before with "ipconfig /release6 <interface>".

So on Windows always do the following for testing in an admin/elevated 
command prompt or Powershell:
ipconfig /release [Name Pattern]
ipconfig /renew [Name Pattern]

If this doesn't help, then deactivate and re-activate the interface via 
netsh to start afresh:
netsh interface set interface <Name> admin=disabled
netsh interface set interface <Name> admin=enabled


> By the way:
> Does dnsmasq also send a RA for the second/GUA dhcp range? How can I 
> avoid this?
> I would prefer to handle RA settings per dhcp-range via tags.

Yes, sends RA for each IPv6 DHCP range it manages. Couldn't find an 
option to disable or enable it for a specific dhcp range.
Additionally if a dhcp range is defined multiple times, it also sends 
the RA multiple times.
Will create to feature requests for these issues in separate posts.


> Configuration:
> 1. File /etc/default/dnsmasq (Debian specific)
> #DOMAIN_SUFFIX=`dnsdomainname`
> #DNSMASQ_OPTS="--conf-file=/etc/dnsmasq.alt"
> ENABLED=1
> CONFIG_DIR=/etc/dnsmasq.d,.dpkg-dist,.dpkg-old,.dpkg-new
> IGNORE_RESOLVCONF=yes
> 
> 2. dnsmasq configuration
> # IPv4 options: router, dns, ntp
> dhcp-option=tag:lan4,3,10.0.0.254
> dhcp-option=tag:lan4,6,0.0.0.0
> dhcp-option=tag:lan4,42,10.0.0.254
> 
> # IPv6 options: dns, domain
> dhcp-option=option6:dns-server,[fd00::]
> dhcp-option=tag:ula6,option6:domain-search,local.domain
> 
> dhcp-authoritative
> domain-needed
> strict-order
> no-resolv
> localise-queries
> bogus-priv
> expand-hosts
> local-service
> domain=local.domain
> local=/local.domain/
> addn-hosts=/etc/hosts.static
> addn-hosts=/etc/hosts.block
> stop-dns-rebind
> rebind-localhost-ok
> dhcp-broadcast=tag:needs-broadcast
> 
> server=10.0.0.254
> 
> ### IPv4 range
> dhcp-range=set:lan4,10.0.0.100,10.0.0.199,255.255.255.0,12h
> 
> ### IPv6 ranges
> dhcp-range=set:ula6,fd7a:d:e:f::1:0,fd7a:d:e:f::1:ffff,64,12h
> dhcp-range=set:gua6,2003:a:b:c00::1:0,2003:a:b:c00::1:ffff,static,64,12h
> enable-ra
> 
> dhcp-host=00:50:56:39:1d:3e,10.0.0.50,[::32],test-machine
> 
> Kind regards
> Maddes
> 
> [1] Telekom native IPv6 Internet connection
> IPv6 prefix: 2003:a:b:c00::/56 (c|00 = 256 subnets possible)
> IPv6 adresses: 2003:a:x:y:1:2:3:4 (External IPv6 address from ISP 
> subnet)
> 
> [2] Unique Local Addresses
> ULA: fd7a:d:e:f::/64
> 
> [3] Router AVM FRITZ!Box 7490
> FRITZ!OS: 06.83 (German)
> DHCPv6 for LAN: Off
> Standard-Gateway for Internet: On
> DNS via RA: Off (RFC 5006)
> RA: Enabled with M and O flag, SLAAC allowed (=A flag); DNS not 
> advertised
> https://en.avm.de/service/fritzbox/fritzbox-7490/overview/
> https://en.avm.de/products/fritzbox/fritzbox-7490/
> 
> [4] Raspberry Pi 2
> OS: Raspbian, Derivative of Debian 8 "Jessie", build from Raspberry Pi 
> Foundation
> https://www.raspberrypi.org/products/raspberry-pi-2-model-b/
> https://www.raspberrypi.org/downloads/raspbian/
> https://www.raspbian.org/