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I had AI write a script to analyze Caddy logfiles to see the ratio between IPv4 and IPv6 for this blog. IPv4: 58.51% IPv6: 41.49% Over the weekend I’ll work on some fail2ban rules to keep bots and (wordpress) junk out. Let’s see if this changes.
In a previous post I wrote that I started a gofundme to produce an IPv6 related tutorial series on YouTube, accompanied by blog posts, slides, labs and contributions to other projects like https://github.com/becarpenter/book6/ All videos will max. 20min, add free and I will reject any non relevant sponsoring. Here are my ideas for the first 10 lessons (subject to change), not all off them strictly…
Based on another “IPv6 is bad” post on mastodon I diced it’s finally time: https://gofund.me/49dd0f9c9 Fund me to produce an IPv6 related tutorial series on YouTube, accompanied by blog posts, slides, labs and contributions to other projects, e.g. https://github.com/becarpenter/book6/
It’s been a while but I just update the IPv6-Resources list on gitlab. How to contribute create a merge / pull request (prefred) create an Issue mark commerical products, like books, training and tools mark links that are not in English
If you want (or in my case have too) test some stuff with SLES and network equipment, you just can add a SLES container to your ContainerLab lab: name: suse-lab topology: nodes: suse: image: registry.suse.com/suse/sle15:latest kind: linux One clab deploy later and you can access your SLES container: root@clab:~/suse-lab# docker exec -ti clab-suse-suse bash suse:/ # uname -a Linux suse…
When you search the internet on how to use net-snmp with IPv6 most of the examples you’ll find look like this: snmpwalk -v2c -c lab udp6:[3fff:172:20:20::5] | head -1 iso.3.6.1.2.1.1.1.0 = STRING: "Arista Networks EOS version 4.35.0F-44178984.4350F (engineering build) running on an Arista cEOSLab" TIL: Apparently since version 5.7 you can just use snmpwalk -v2c -c lab 3fff:172:20:20::5 |…
What’s done wrong here? $ curl foo.example.com curl: (6) Could not resolve host: foo.example.com $ host foo.example.com Host foo.example.com not found: 3(NXDOMAIN) $ ping foo.example.com ping: foo.example.com: Name or service not known $ traceroute foo.example.com foo.example.com: Name or service not known Another admin trying to be thorough when reporting an issus. They could have stopped…
If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. But it has to look, swim, and quack like a duck. If it only does one or two, it might be something else entirely. Almost two years ago I opened a ticket on GitHub because I couldn’t (and still can’t) install packages via pip on an IPv6-only host with an IPv6-only resolver. Fastly is used as a CDN, and…
I recently looked at a curriculum for a basic level course of a well known vendor. What struck my eye was that IPv4 basics, including classes, was pretty high on the list of topics. Then I found stuff like RIP version 1 in the list of topics an IPv6 almost at the end of the list of topics. My calendar says it’s the End of 2025 so IPv6 should be at least as important as IPv4. IPv4 classes…
This is another post that started after several toots on mastodon. Most of the things presented here were already tooted by other people, but I think this is a good chance to write a mini tutorial about what to look at. We’ll use DNS, whois, BGP and your favourite search engine. What is DNS4EU? To quote the web page: Supported by the European Union Agency for Cybersecurity (ENISA), the…
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…
Just so I find it again when I run across the same problem in the future: I wanted to log in to one of my servers and couldn’t access it, because I couldn’t resolve the name from one specific domain. All other domains worked fine. So let’s head over to the DNS server and check what we can do. I’m running BIND, and it ships with two tools, named-checkconf and named-checkzone…
Another troubleshooting tale. When you look at the following output, what is your first guess? root@mail:~# postqueue -p -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- D94947FBE83 1331 Thu Apr 3 15:18:58 jens@example.net (Host or domain name not found. Name service error for name=example.com type=MX: Host not found, try again) foobar@example.com DNS right? Nope! Well kind off.…
In another blog post I wrote that I’m using make to restart BIND and showed the following example: root@dns:/etc/bind# cat Makefile all: /usr/sbin/named-checkconf -z /usr/sbin/rndc reload The all in the above Makefile is the default target used when calling make without options. The second line (Note that there is a TAB ) runs a bind tool called named-checkconf with the option -z to check…
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…
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…
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. June 5th 2012, around five in the afternoon 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)…
One of my lasts posts made it to Hacker News . Some people asked if the server survived. Yes it did, just a little more traffic:
In my last post , which made it to Hacker News , I wrote: "HE can have some funny side effects. In a project a connection to a development web server sometimes worked and sometimes didn't. The solution was quite simple. The customer used a split VPN tunnel. IPv4 was routed via the VPN tunnel and those IPv4 addresses were allowed in the web servers access list. IPv6 was routed via the normal…
Yesterday I read this toot (German) over on mastodon which starts with “IPv6 is hard.” No it’s not. It’s different. I ran across this multiple times: There is an A and an AAAA-record for a FQDN, but the web server is only reachable via IPv4. You can easily test this with curl $ curl -4 https://github.com -o /dev/null % Total % Received % Xferd Average Speed Time Time Time…
CLAT in Linux Networkmanager DNS delegation jc - Convert command output to json Stratoshark - Analyse syscalls curl from start to end Security Bingo Linux Routing Fundamentals Packet where are you nftable-tracer
https://github.com/ipinfo/cli [https://blog.sdn.clinic/2025/03/wireguard-and-vrfs/9(https://blog.sdn.clinic/2025/03/wireguard-and-vrfs/] https://github.com/girishji/pythondoc.vim
Some time ago I asked on Mastodon if someone would be interested in a series of videos about IPv6. Some people are, so I’ll give it a try. Each video will be accompanied by a blog post. This blog post and other materials will be available on gitlab. Starting in January 2025, videos will come out every Tuesday evening (CET) and I’ll try to keep them between 10 and 20 minutes.
Last week I talked about ContainerLab at our admin meetup in Berlin. Containerlab provides a CLI for orchestrating and managing container-based networking labs. It starts the containers, builds a virtual wiring between them to create lab topologies of users choice and manages labs lifecycle. As allways the presentation was streamed and recorded. Talk was in German, slides are in English: Recording…
The basic Idea: What if we put together an “advent of IPv6” just like – https://adventofcode.com/ or https://tryhackme.com/r/christmas Gitlab repo including my slides from RIPE89 https://gitlab.com/jenslink/advent-of-ipv6 There is also a mailing list: https://list.sys4.de/postorius/lists/ipv6-advent-orga.lists.quux.de/
You want to make a presentation, write a blog post or document your brand-new software. What do you use as domain-names, IP addresses and AS numbers? If you are documenting your systems or a setup you build for a customer the question is easy to answer: It’s best to use the actual data. But if you are writing a more generic documentation there are some reserved domain names, IP prefixes and…
Welcome to my new blog. Yes, a new blog at the end of 2024. Since the last post in my old blog in February 2019 I moved to the other side of Berlin, worked on several interesting projects and accumulated quite a lot of ideas of things I should document or learn about and then document. What to expect? So as I’m an old nerd, who is using Linux since he first got it an 35 3.5" floppy disks 1 ,…
About me Nerd Freelance IT-Consultant with more than 25 years work experience Started with Linux when it was shipped on 35 3.5" floppy disks DNS since 2000 Switching / Routing since 2002 IPv6 since 2007 What I do Consulting / Administration: IPv6 / DNS / Network / Linux Automation (mainly Ansible today) Monitoring (Prometheus / Grafana, Icinga2, LibreNMS) Linux and network administration…
Contact / Imprint email: info@jenslink.net Address Jens Link Delbrückstr. 41 12051 Berlin Links Github Gitlab LinkedIn Mastodon YouTube Disclaimer No cookies (in case someone is missing the warnings), no external content, logfiles will be kept for five days.