A short one, also via mastodon:
host deutschehochschule.de
deutschehochschule.de has address 162.159.134.42
deutschehochschule.de has IPv6 address ::ffff:162.159.134.42
deutschehochschule.de mail is handled by 0 deutschehochschule-de.mail.protection.outlook.com.
“Of course we have IPv6”. BTW: The IPv4 address is from Cloudflare. AFAIK: You have to actively do something not to do proper IPv6 using Cloudflare.
Some shameless advertising:
If you need some help with IPv6, DNS, Linux, Automation and related stuff feel free to contact me. I’m available for about two days a week, remote preferred.
Yet another Mastodon-inspired post. In this toot the author reports that downloading python packages is slow, and the Internet said that disabling IPv6 is the solution.
Slow can mean two different things here. If the host I’m using has a globally unique IPv6 address, but my connection to the outside is broken somehow, most software would try IPv6 first and then, after a timeout would fall back to IPv4 and try again. It can also mean that the IPv6 connection is working, but the download is actually slow.
Some time ago I was asked why IPv6 wasn’t working. The customer had just configured some ip6tables rules and IPv6 stopped working. See if you can spot the error in the following example rule set:
ip6tables -A INPUT -p ICMP -j ACCEPT
ip6tables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -p tcp --dport ssh -j ACCEPT
ip6tables -A INPUT -j DROP
The mistake is in line one. In IPv6 neighbor discovery and other functions rely on ICMPv6 which is a different protocol then ICMP. Some how ip6tables is fine with loading the ICMP protocol.
Last year I did a presentation about my 1st IPv6 project. After writing a post titled IPv6 is hard, where I told people that they shouldn’t do IPv6 if they don’t take it seriously, here is a post about how it can be done.
The team lead walks into the office with a crate of beer and asks if we are done with the IPv6 project. We are (we think) and have a beer.