I wanted to learn a little more about IPv6 subnets so I started using HE tunnel broker and they gave me a /48 as I wanted to mess around with subnetting with IPv6. As far as I am aware from reading in this forum that you aren’t really allowed to choose the subnet and when you assign the address to the interface it’ll automatically select one for you for each interface. I’ve come into things like this where it’ll choose a number for the subnet and increment it 1-2 times before actually using it.
So I end up with something that looks like this
Any ideas on what might be going on here in regards to why the subnets aren’t sequential and appear to be skipping? Thanks.
Prefixes are handed out by pool sequentially. And ROS somehow remembers their assignment … which is good because generally same prefixes are reassigned to same interface (e.g. after reboot). So it seems that while you were playing (or should we say: learning), some prefixes were assigned to interfaces which are no longer present on router? Well, ROS did remember about that. Most probably those unused prefixed would get recycled after all prefixes are handed out (for the first time). Which, with /48 prefix, means after you use up all 4096 /64 prefixes. At least that’s my experience.
Fixating on exact prefix number is, IMO, not productive. With SLAAC the host part (the least-significant of /64 prefix) will be pseudo-random anyway, so IPv6 address of host is in this case hardly usable to configure in FW rules. So for device, which offers service to internet, one would have to set IPv6 address manually (or by issuing static DHCPv6 lease, which is not yet fully supported in ROS) and in this case having the whole prefix delegation stuff (which in principle doesn’t guarantee immutable prefix) means major hassle. My first-hand experience is that even with my ISP giving me static prefix, they changed it after I upgraded from xDSL to GPON (even though they use PPPoE to deliver internet and my IPv4 address remained unaltered during upgrade).
Thanks for the reply, I haven’t touched the addresses since the photo as I became busy and just today started fiddling with it and noticed the addresses automatically became sequential. I feel this is bad as my prefix is static but if Mikrotik is dynamically changing my subnet this would cause problems with DNS, etc. Do you know why this might happen? After a power outage or automatically overtime?
Currently, whenever you make a tiny change to the configuration of the (underlying) bridges or the VLAN interfaces, those affected interfaces (if you change a bridge, all attached VLAN interfaces are affected too) will all drop their currently assigned prefixes and the router pick new prefixes for them from the pool. That’s the reason why you saw those gaps in your previous screenshot. You can open the property of a bridge and toggle DHCP Snooping for instance, to see it happens. Or one VLAN interface and change ARP mode (although unrelated to IPv6).
Ahh that’s unfortunate, hopefully one day Mikrotik will give us the ability to manually configure subnets or at the very least allow the option for a automatically assigned static subnet.
Just color me confused; I manage my Hurricane Electric /48 tunnel with static commands and without an address pool which suggests in your case an address pool is mandatory?
Pool isn’t mandatory for static assignments, it’s optional and just a convenience for distributing addresses. HE’s IPv6 assignment is static so you can manage it statically as you do. Other folks are using their HE tunnel to learn about IPv6 for when their own ISP does make it available in the future. Consumer/residential users are much more likely to receive a prefix from their ISP through IPv6 Prefix Delegation which will end up in a pool. So it’s OK to manage your prefix through a pool if you would like to gain some experience and learn how to operate with a PD-assigned prefix.
I am pretty new to IPv6 so I wasn’t sure how to setup the interfaces, a lot of the instructional videos I watched used pools in their videos so I believe that’s what stuck with me. I never actually tried a static assignment but reading your comment made me question why I never have. I just now changed it to static so that should take care of any quirks. Thanks!
You’re welcome. IPv6 routing with single provider works with just the main routing table.
If ISP deploys IPv6 and keeping Hurricane Electric is wanted, 2nd routing table for policy routing works.
I use VLAN segmented network but VLAN is optional; drop my VLAN stuff and replace vlanNNN with real interfance names:
