IPv6 address "incrementing"?

[breakaway]

I have a rb750gr3 running 7.21.2 (latest at time of writing) an I’m running into a really irritating issue with IPv6 I can’t seem to solve.

My internet comes in via PPPoE for ip4 connectivity; ipv6 is via a dhcp client, configured like so:

/ipv6 dhcp-server add interface=bridge name=LANPrivate-dhcp6-server prefix-pool=delegation

/ipv6 dhcp-client add add-default-route=yes custom-iana-id=0 custom-iapd-id=0 default-route-tables=main interface=WAN pool-name=delegation prefix-hint=::/56 request=prefix use-peer-dns=no

I receive a /56 delegation from my ISP. I then break it into /64s for each of my internal LANs. Currently, I have only one LAN (on the "bridge") so the address assigned like this:

/ipv6 address add address=0:0:0:0:: from-pool=delegation interface=bridge

This gives me an address like

2001:db8:abcd:400::/64

on my "bridge", and this set up has been working great for several years now.

But now, for a about 8 hours or so this works fine, then, the ipv6 address "increments", i.e. becomes

2001:db8:abcd:403::/64

If I remove this address manually, and attempt to re add 2001:db8:abcd:400::/64, It comes up with 2001:db8:abcd:404::/64(increments by one). This goes on forever.

I have tried everything from tweaking various settings to removing IPv6 completely, rebooting, waiting 1hr, the adding it back but it the above behaviour is still observed.

This is a rb750gr3, but i have observed similar behaviour on my rb5009 running 7.21.2 as well. It seems like something in Mikrotik’s IPv6 handling has changed? What is causing it, and how to resolve it?

[breakaway]

I see this is a long standing issue.

Order of DHCP delegation assignment

My IPv6 comes from Comcast via a /56 allocation over DHCP: /ipv6 dhcp-client add add-default-route=yes interface=ether1-gateway pool-name=comcast-ipv6 request=prefix /ipv6 dhcp-client print Flags: D - dynamic, X - disabled, I - invalid # INTERFACE STATUS REQUEST PREFIX 0 ether1-gateway bound prefix 2603:1234:abcd:x000::/56, 3d56m56s /ipv6 pool print Flags: D - dynamic # NAME PREFIX …

[CGGXANNX]

Pinning the subnet id is supported in 7.21. You only have to remember to not use the subnet id 0. See:

Experiences with ipv6?

You can specify the subnet id part since 7.21, no need to specify the full address. However there is one exception, that is the first subnet (the one with subnet id all zeros) cannot be specified that way, that one will be dynamic. You can read about this in the 7.21 threads. Example: ISP gives you /56 prefix, that you put in isp-pool, under /ipv6 address, you can assign hardcoded prefixes like this, together with from-pool=isp-pool: address=::1:xxxx:yyyy:zzzz:www address=::2:xxxx:yyyy:zzzz:w…

In your case, assign the /ipv6 address entries for your interfaces like this:

• 0:0:0:1::1/64 or ::1:0:0:0:1/64
• 0:0:0:2::1/64 or ::2:0:0:0:1/64
• ...
• 0:0:0:f::1/64 or ::f:0:0:0:1/64
• 0:0:0:10::1/64 or ::10:0:0:0:1/64
• 0:0:0:11::1/64 or ::11:0:0:0:1/64
• ...
• 0:0:0:fe::1/64 or ::fe:0:0:0:1/64
• 0:0:0:ff::1/64 or ::ff:0:0:0:1/64

Which means you assign 0000:0000:0000:00nm:xxxx:yyyy:zzzz:wwww with nm ≠ 00 and the subnet will not move. Just don't assign ::xxxx:yyyy:zzzz:wwww because the subnet-id will then be 00 and the assignment will be dynamic and jump around every time the DHCPv6 binding is renewed.

[pe1chl]

Today I got a reply on my ticket that this subnet 0 problem “will be fixed in a future release” and my ticket was closed, of course we have to wait for that future release.