IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6, 2nd Edition
Taken from a previous comment I’ve made re IPv6:<p>IPv6 is fundamentally not ready for real world use within small&#x2F;medium businesses and homes IMO. At least not without NAT. Why?<p>- Can’t just simply put one IPv6 router&#x2F;firewall behind another. Not all IPv6 routers support DHCP-PD, and even if they did, you could have 2-3-4 levels of routers&#x2F;firewalls at a business. I’m not making this up- retail&#x2F;gas&#x2F;food industries often have a plethora of networks at a location, and the business&#x2F;franchise owner is not tech literate, or even if they were, the equipment is managed by third party vendors and they don’t want to customise their IP network for each location. It makes for messy deployment and maintenance.<p>- Can’t just simply open a firewall rule on the main site router to forward say HTTPS to an internal service. Why? Not all ISPs give static IPv6 prefixes, not all PCs&#x2F;servers&#x2F;devices support DHCP6 for static leases, and then there’s IPv6 privacy addresses. Yes, you can statically configure (only if ISP is static too!). No, I don’t want to open the port to all devices on the LAN and no I can’t rely on each device to be running their own firewall (let alone a properly configured one!).<p>- WAN failover &#x2F; multiple ISPs is hard. You have a fibre primary feed, and a secondary cellular&#x2F;5G feed. Each has different IPv6 addresses. How do you ensure the right ISP is used at any given point? IPv6 shifts this decision to the client. This makes load balancing and policy based traffic routing (eg VoIP over fibre 1, FTP over fibre 2, etc). Also the cost of using a multi-homed IPv6 subnet &amp; BGP in a SME&#x2F;retail business is out of the question (plus the cellular ISP wouldn’t support it anyway).<p>All the above works fine out of the box with IPv4 and NAT. It’s bread and butter easy. At the cost of not having dedicated unique public IPs but these places simply don’t need them.<p>What IPv6 should have done to ensure a smooth migration is allowed for NAT from the very start. That would have let everyone who needed public IPs get them straight away, and those that didn’t to still migrate anyway with as little drama as possible. But it’s just not the case, NAT has been slowly added but it’s support is far from ubiquitous that IPv4 has.