I have a server which responds differently to requests from the general internet as opposed to the intranet. For IPv4 I can simply check if the address begins with 192.168. This works for my needs. What is the equivalent for IPv6?
2 Answers
First of all "intranet" is not limited to 192.168. There are 3 private networks defined in RFC-1918: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.
In IPv6, it is called a Unique local address: and covered in RFC-4193 -- all addresses matching FC00::/7. Basically, you should be able to search for IPv6 addresses starting with fc or fd.
The “intranet” is your local subnet, ie. your servers address/64. IPv6 RFCs strongly discourage networks smaller than /64, so it’s unlikely you’ll encounter any.
While there are link-local addresses, they aren’t really relevant here, because you wouldn’t use them.
An additional ULA network might be an option, although it poses additional management overhead.
