On 19/06/19 2:11 AM, Reco wrote: > Hi. > > On Tue, Jun 18, 2019 at 11:47:08PM +1200, Richard Hector wrote: >> On 18/06/19 10:32 PM, Reco wrote:
>> >> Custom routes? When routing between 2 networks using the same range, >> either with a VPN or some kind of direct connection? It's going to need >> some evil double NAT sorcery, especially if the same actual addresses >> are in use on both. > > As long as: > > a) It's L3 VPN, so ARP is not a concern. > b) There are no duplicate IPs on both sites combined. > > The problem can be 'solved' by announcing specific IP routes to each and > every host on both sites. Yes, it's gross. Eww. And people who have chosen 'obvious' blocks (like 192.168.1.0/24) are probably going to start numbering at the bottom, too. So duplicates are almost inevitable. I think we agree here. > >>>> There are online random ULA generators - but I'm not convinced one of >>>> them didn't give me the same block twice, or whether it was my own error. >>> >>> Never used one. IPv6 /8 block consists of 2^56 unique /64 subnets. >>> Surely it's possible to choose several unique /64 subnets by using, say, >>> ipv6calc. >> >> Yes, but there is a recommendation to use random ones, and even a >> suggestion of how to do it, in RFC 4193. > > But this RFC's "random" cannot mean "I start each day with selecting > new, custom /64 IPv6 ULA prefix for my site". ipv6calc fills this > nicely, try it some day. Every day? Of course not. Just when you set up a new network. I made the mistake of doing it for every subnet, which is unnecessary; I should have generated one /48 and split that up manually - and probably simplified my (static) routing. I should get round to renumbering one day ... though I now have a real /48 from one of my VPSs to use for some of it. Richard
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