IPv6 DHCPv6 + SLAAC, only provide SLAAC to not preserved DHCP adresses.



  • Dear reader

    So I've setup DHCPv6 for my workstations and my Servers, they do get the right IP's but also get a SLAAC ip which they use as their main IP.
    Is there a way (possibly modify the code maybe) to make it so that clients that have a static IPv6 set through DHCPv6 do not get SLAAC info and those who are not on the list don't?

    If not: Is there a way to 'prefer' a DHCPv6 IPv6 address over the SLAAC one? The only reason I'm using SLAAC is because Android devices on my network do not support DHCPv6.

    Thanks in advance

    • Wraptor

  • Netgate

    Seems that whatever source address the clients use is up to the client. It is also up to the client whether or not they also grab a SLAAC address in addition to the DHCPv6 address and, further, up to the client whether they also get/use temporary addresses via SLAAC.



  • Most desktop operating systems (Windows, Mac, some Linux) will use both SLAAC and DHCPv6 IP Addresses if your RA is set to "Assisted"… they'll usually default to the SLAAC address for outbound connections (since they also use SLAAC privacy extensions), but will accept inbound connections on both addresses (unless a server process is configured specifically for one address).

    Other devices (like some network printers) may only use DHCPv6 if it's available, and SLAAC if it's not. Again, this assumes an "Assisted" RA, since that allows for both IP address assignment methods. "Managed" will be DHCPv6-only (which means no Android devices on IPv6, since they don't use DHCPv6)... "Unmanaged" is SLAAC only.

    A note that Windows 10 has a known issue with DHCPv6 if you have the Anniversary Update from August 2016 installed.



  • I am aware of the Windows 10 DHCPv6 Issue since my workstation, Windows server 2016 and gaming system are having issues with it, I've just set the lease time to a week and setup my servers to manually renew every day with a windows task.

    Isn't there a way to make the router tell the client that has a preserved IPv6 address through DHCP that the router is in managed mode, and in SLAAC mode to all the other clients?



  • @Wraptor:

    Isn't there a way to make the router tell the client that has a preserved IPv6 address through DHCP that the router is in managed mode, and in SLAAC mode to all the other clients?

    Nope. This "mode" is a series of flags in the router advertisement that is sent to all devices on the network. There's no way to customize the RA from device to device.



  • Ok thanks for the help.
    I guess It'll do as is then… :Þ


  • Banned

    You'd have to stick the managed clients on a separate VLAN and set the RA as "Managed" there.



  • FYI regarding the Windows 10 Anniversary DHCPv6 renewal issue… according to the very last post in  this MS Technet discussion, the fix will be in the March 2017 monthly update.