Tag Archives: Internet

NTP Filtering (Delay & Blockage) in the Internet

NTP (Network Time Protocol) messages are sometimes rate-limited or blocked entirely by Internet operators. This little-known “NTP filtering” was put into place several years ago in response to DDoS (Distributed Denial of Service) attacks. NTP filtering may drop NTP messages based on rate or message size. Let’s dig into it: Continue reading NTP Filtering (Delay & Blockage) in the Internet

Adding your NTP Server to the NTP Pool Project

You have a running NTP server with a static IP address? What about joining the NTP Pool project by adding your server to the pool? You will give something back to the Internet community and feel good about it. ;)

It doesn’t matter if you’re running a Raspberry Pi with GPS/DCF77 on your home, or a fully-featured NTP appliance such as the ones from Meinberg on your enterprise DMZ. Just a few clicks and your server will be used by the NTP Pool’s round-robin DNS. Here’s a simple tutorial:

Continue reading Adding your NTP Server to the NTP Pool Project

My IPv6/Routing/Cisco Lab Rack (2019)

My lab rack of 2019 consists of multiple Cisco routers and switches, as well as Juniper ScreenOS firewalls for routing purposes, a Palo Alto Networks firewall, a Juniper SRX firewall, a server for virtualization and some Raspberry Pis. That is: This rack can be used for basic Cisco courses such as CCNA or CCNP, or for even bigger BGP/OSPF or IPsec VPN scenarios since those ScreenOS firewalls are perfect routers as well. Of course, everything is IPv6 capable. Having some PoE-powered Raspberry Pis you can simulate basic client-server connections. A Juniper SA-2500 (aka Pulse Connect Secure) for remote accessing the Lab rounds things up.

I am just writing down a few thoughts on why I have “designed” the rack in that way. It’s basically a reminder for myself. ;)

Continue reading My IPv6/Routing/Cisco Lab Rack (2019)

Urlaub ohne Internet & Smartphone – ein Traum!

Zum wiederholten Mal habe ich es getan: Ich war zwei Wochen mit der Familie im Urlaub – und zwar ohne Smartphone, ohne Tablet, ohne Notebook, ohne Fernseher. Offline! So ganz. 14 Tage lang. Und das war auch gut so. Urlaub eben.

Also zumindest so, wie ich es wirklich als Urlaub wahrnehme. Und meiner Meinung nach auch die einzige Möglichkeit, in unserer heutigen Zeit wenigstens einmal im Jahr ganz abzuschalten.

TL;DR: Smartphone zu Hause lassen -> Urlaub wieder zur Zeit des Ausruhens machen!

Continue reading Urlaub ohne Internet & Smartphone – ein Traum!

Internet’s Noise

If you are following the daily IT news you have probably seen many articles claiming they have scanned the whole Internet for this or that. Indeed there are tools such as the ZMap Project “that enable researchers to perform large-scale studies of the hosts and services that compose the public Internet”.

This time I was not interested in scanning something, but in the question about “how many scans happen during one day on my home ISP connection?” Or in other words: What is the Internet background noise as seen by almost any customer? For this I sacrificed my Internet connection at home for 24 hours, while a factory-resetted router established a fresh Internet connection (IPv6 & IPv4) without any end devices behind it. No outgoing connections that could confuse or trigger any scans. That is: All incoming connections are really unsolicited and part of some third-party port scans, worm activities, or whatever. Using a network TAP device I captured these 24 hours and analyzed them with Wireshark.

In this blogpost I will present some stats about these incoming port scans. Furthermore I am publishing the pcap file so you can have a look at it by yourself.

Continue reading Internet’s Noise