I'm trying to understand the following statement from the OpenVPN manual.
In a routed setup, you cannot use your on-link network; you must use a unique routed network range, just like when routing with IPv4.
In short, this is saying that to run IPv6 through open VPN (without hiding it behind a NAT) you need to have two IPv6 /64 blocks. Or at least one block and a completely separate IPv6 address.
Can anyone explain why this is?
I'm struggling to get my head round this as I have a server with a /64 block assigned to it. From the network's point of view all traffic in that block must be sent to my server (?). On that server all traffic to that block would be sent via VPN if not its own IP. From the VPN client's point of view all traffic to that block would be sent via VPN if not its own IP.
I can't see why having the same /64 block assigned to two interfaces would cause a problem where the entire block is assigned to one server.