ICMP ‘Destination Unreachable’ Messages @ SharkFest’24 EU

Conference Talks, Internet Access, Network, Wireshark, , , , , , ,

I did a presentation at SharkFest’24 EU in Vienna, the “Wireshark Developer and User Conference“, about the topic: “Unveiling Network Errors – A Deep Dive into ICMP ‘Destination Unreachable’ Messages“. It covers the following:

“Effective troubleshooting of network issues is a critical concern for network technicians. While many are familiar with basic ICMP tools like ping and traceroute, the breadth of ICMP capabilities often goes underutilised. This session delves into ICMP messages, specifically the ‘Destination Unreachable’ type, and the insights they provide into network errors.

We will explore methods for capturing and analysing network traffic, highlighting practical tips and tricks for using Wireshark to diagnose and resolve issues efficiently. Attendees will gain a deeper understanding of ICMP message functions and how to leverage them for improved network troubleshooting.”

You can watch the whole session and download the slides. And you can do the six challenges at the end of the session as well. (The answers are not in the PDF, but shown in the video.)

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Security-as-a-Podcast

Conference Talks,

Es ist so weit – mein Kollege Florian und ich haben einen Podcast gestartet! 🎉

Der Security-as-a-Podcast beschäftigt sich mit Netzwerksicherheit – aber nicht im klassischen „Wir erklären euch die RFCs“-Stil, sondern eher aus der Perspektive von zwei Menschen, die selbst regelmäßig mit Security-Buzzwords bombardiert werden und manchmal nur halb wissen, worum es wirklich geht.

Begriffe wie SASE, ZTA oder OT begegnen uns im Alltag ständig – in Projekten, in Meetings, auf Konferenzen. Doch wie oft bleibt davon wirklich was hängen? Und was davon ist mehr Marketing als Substanz?

In unserem Podcast sprechen wir genau darüber – miteinander und mit Experten. Ziel ist es, Wissen zu entwirren, einzuordnen und so aufzubereiten, dass es greifbar und verständlich wird – und im besten Fall auch im Kopf bleibt. Vom Business-Case hin zum Tool.

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Editing Palo Configs by Scripts: pan-os-php

Palo Alto Networks, , , , , , ,

There are recurring cases where tasks cannot be edited quickly and easily using the classic Palo Alto Networks GUI or Panorama. For example, editing multiple policies at once, such as during a zone migration. Or checking which policies haven’t log forwarding enabled, hence enabling it directly. Or finding unused objects, including deleting them.

For these situations (and many more!), there’s a tool with a wealth of predefined scripts: pan-os-php. This first blog post covers installation and some initial use cases.

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Azure PTP Accuracy

Microsoft Azure, NTP, , ,

The Network Time Protocol (NTP) is widely used to synchronize computer clocks. The Precision Time Protocol (PTP) can be used as a time source as well, which is expected to be accurate within microseconds. However, at Microsoft Azure VMs, PTP-derived time-of-day errors could exceed 50,000 microseconds, which may be inadequate. Let’s go into some details:

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Bad IPv6 Approaches

IPv6, , , , , , , , , , ,

I just got a few emails from an administrator of a medium-sized company, asking some IPv6 questions. They want to use IPv6 to reach the Internet, using two ISPs, while remaining IPv4-only on their internal networks. For whatever reason, they came across three different ideas that were almost completely wrong, speaking of a sound IPv6 design. But why? Maybe because IPv4 thinking is a bigger problem than we ever thought? Or because admins rely on firewall vendors (like Fortinet) that suggest completely wrong network approaches?

Let’s dig into some misconceptions concerning IPv6:

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Palo Alto Networks Announces Strategic Shift to Apparel Manufacturing

Palo Alto Networks, , , ,

Palo Alto Networks, a global leader in cybersecurity solutions, has announced a significant strategic shift. The company will transition from its core cybersecurity business to exclusively focus on apparel manufacturing.

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Path MTU Discovery

Internet Access, Network, Routing, , , , , , ,

One of the mysteries for me in IP networks was the Path MTU Discovery (PMTUD) process. I’ve seldom seen any problems with the MTU at all. Fortunately, while troubleshooting some router issues, I captured several ICMP “packet too big” errors along with the original packets. 👍🏻

Let’s have a look at those PMTUD processes for IPv6 and legacy IP with Wireshark. Of course, these captured connections are part of the Ultimate PCAP as well, hence, you can download the most current version of it and analyze it by yourself.

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Which KPIs to monitor on a Palo Alto Firewall?

Monitoring, Palo Alto Networks, , , , , ,

We wanted to monitor some of our Palo firewalls from our monitoring system via the API. But: Which enhanced metrics/KPIs shall we monitor? While there are some obvious ones such as interface counters, uptime, software versions, license expiry dates, or HA-states, we dug a little deeper to get more out of it, such as mgmt-/data-plane stats, packet rates, drop counters (all global counters?), and routing entries.

Here are some ideas on which values a monitoring system could observe. I’m listing the required API calls along with some demo values that can be used to develop monitoring tools/scripts.

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Dual-Stack PPPoE on a FortiGate Firewall

Fortinet, Internet Access, IPv6, , , , , , ,

You can use a FortiGate to connect to the Internet (that is: Dual-Stack!) directly in various ways. In my current setup, I’m using a PPPoE residential xDLS connection. It’s not that easy to configure everything correctly since it requires the use of many different protocols such as PPPoE and PPPoEv6 (PPP IPV6CP) along with DHCPv6-PD. But here it is:

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DHCPv6 Prefix Delegation on a FortiGate Firewall

DHCP/DHCPv6, Fortinet, IPv6, , , , , , ,

I got DHCPv6-PD aka prefix delegation up and running on a FortiGate. Yes! ✅ Configuring it is tricky since it’s not always clear which options to use. You cannot see everything in the GUI (it even changes depending on other options made later on or selects hidden and wrong default values), hence, you must set specific options via the CLI. I navigated around some bugs and finally got it running. Here we go:

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Dual-Stack PPPoE on a Palo Alto Firewall

Internet Access, IPv6, Palo Alto Networks, , , , , , ,

If you want to establish an Internet connection (that is: IPv6 and IPv4) right away from your firewall through xDSL connections, you need quite some technologies: PPPoE and PPPoEv6 (PPP IPV6CP) along with DHCPv6-PD. Fortunately, with PAN-OS 11.0 and 11.1, those missing IPv6 links were finally added by PANW to their Strata firewalls. (I have been awaiting them since 2015!)

So, here it is: Connecting a Palo through an xDSL modem to a residential ISP:

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xDSL-Modems

FRITZ!Box, Internet Access, , , , , ,

Wenn man eine Enterprise-Firewall an einem klassischen DSL-Anschluss verwenden möchte, benötigt man ein extra DSL-Modem. Dies unterscheidet sich von Heimkundenroutern wie der Fritzbox, die immer schon ein DSL-Modem mit eingebaut hat. Back to the roots – so wie damals, als man ein Dreiergespann aus Splitter, Modem und Router hatte – kennt ihr es noch? ;)

In meinem Fall wollte ich eine Palo bzw. Forti an einem Telekom VDSL-Anschluss betreiben. Zwei Varianten habe ich getestet: Eine zum Modem degradierte Fritzbox (Bastellösung) und ein reines DSL-Modem aus dem Hause DrayTek. Hier ein paar Notizen und Screenshots:

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Das Domain Name System

DNS/DNSSEC, , , , , ,

Kaum ein anderes Element ist so essenziell für das Internet wie das Domain Name System. Ruckelts mal im DNS, reagieren Webseiten und überhaupt alle Internetanwendungen gleich langsamer oder gar nicht. Doch um Fehlerursachen zu ermitteln und zu beseitigen, brauchen Firmen- und Heim-Admins ein weitreichendes Verständnis der Zusammenhänge.

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It’s Always DNS! @ SharkFest’23 EU

Conference Talks, DNS/DNSSEC, , , , , ,

This time (2023) at the yearly Wireshark Developer and User Conference in Europe, I gave a talk about DNS. How could it have been any different –> The title simply had to be ‘It’s Always DNS‘. 😂

“This session dives deeper into the Domain Name System, covering recursive vs. iterative DNS queries, resource records types, TTL & caching, DNS errors, a little DNSSEC, flags, and of course: Wireshark with its useful display filters, custom columns, colouring rules, and so on. And we will explore some other tools to analyze and troubleshoot DNS even further.”

You can watch the whole session and download the slides. And you can do the six challenges at the end of the session as well. (The answers are not in the PDF, but shown in the video.)

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It’s Always DNS – Poster

At a Glance, DNS/DNSSEC, , , , , , ,

We all know the DNS, right? But when we need to troubleshoot it, it’s getting much more complicated than initially thought. DNS ≠ DNS ≠ DNS. And unfortunately: It’s Always DNS.

To get a better understanding of those different kinds of DNS servers (authoritative vs. recursive), DNS messages (recursive, iterative, zone transfer, …) as well as other techniques (conditional forwarding, DoH, …), I draw a poster to have it all at a glance! Here it is:

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