Has anyone had tried to run an IPv6-only SMTP engine? Pretty much everybody with any sense has IPv6 configured for major front-end servers. I was curious if anyone had tried to run an IPv6-only MTA and received any connection errors.
Is IPv6-only a viable solution yet? Can I expect a few lingering connection issues? Or did a magic fairy come down on the internet and made IPv6-to-IPv4 on port 25 work like magic on a direct connection?
We all know what 127.0.0.1 is used for (loopback).
What are uses cases for the rest of the reserved 127.0.0.0/8 loopback space?
I'm looking for a list of CIDR blocks for "The Internet", i.e. everything from 0.0.0.0 to 223.255.255.255, excluding RFC1918 address space of 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 (yes, I know there are lots of little nets in there that are special, like 192.0.0.0/24, but I really don't care about them). I figure this list must exist somewhere on the Internet, but my google-fu is failing me, so I figured I'd ask here before generating the range myself.
Edit: I forgot a really important part of this question: I need it in the fewest possible number of entries.
And if you want to know what I'm doing with this, we are entering static flow-mods to work around some nasty issues in an OpenFlow controlled network that currently has a significant amount of badness happening, and we need to reduce the number of flow entries temporarily so we don't exceed the available space in the flow tables and cause everything to come crashing down for a few minutes while it reestablishes a connection to the controller.
I am working on a change in a Java EE application that would authenticate based on the user's IP address using ServletRequest.getRemoteAddr. We store IP address ranges (FROM_IP and TO_IP) in a database and the system would authenticate only if a user's IP address falls in a range.
Now, testers have pointed out that digit 0 (zero) should not be allowed in FROM_IP and TO_IP values (in any place). Note that this is an Internet facing application, and so we will get only public IP addresses.
Are testers right in suggesting that validation? Why can't we have zero in the range value such as in 167.23.0.1 - 167.23.255.255?
This is a Canonical Question about IPv4 Subnets.
Related:
How does Subnetting Work, and How do you do it by hand or in your head? Can someone explain both conceptually and with several examples? Server Fault gets lots of subnetting homework questions, so we could use an answer to point them to on Server Fault itself.