Multicast Routing w/ Palo

Palo Alto Networks, Routing, , ,

A rare use case on a Palo (at least from my point of view): Multicast Routing. And it can become as complex as you want. Fortunately, the basics are relatively easy to configure, at least if you have a rough understanding of multicast and routing with PIM and IGMP. (Recommended YouTube session here.) Let’s have a look at the common configuration steps on PAN-OS, the needed security policies to the special destination zone type of “multicast”, as well as some “show” outputs that can be used for troubleshooting:

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Don’t Trust Packet Captures on Firewalls

Packet Capture, , , ,

The other day, I was troubleshooting some network-related stuff, using the built-in Packet Capture on a Palo Alto Networks firewall. And while it did the job at a first glance, I stumbled upon some packets that were simply not correct, read: were not present on the Ethernet cable at all and/or were missing some content.

This proves again what the TAP vendors always claim: Don’t use internal packet captures / SPAN ports at all when you’re really serious about the truth. You MUST use network TAPs!

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OSPFv3 Authentication on a Palo Alto (Logical Router)

Authentication, IPv6, Palo Alto Networks, Routing, , , , , ,

I had a hard time figuring out how to configure OSPFv3 authentication on a Palo Alto Networks NGFW due to its different configuration formats compared to a Cisco router.

TL;DR: The SPI must be set in hexadecimal, while the actual key (40 chars, hexadecimal) must be grouped in 5 sections, separated with hyphens.

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DNS Tunneling: iodine

DNS/DNSSEC, Security, Tutorial/Howto, , , , , , , ,

This post guides through a basic DNS tunneling setup with the usage of the appropriate tool “iodine“. It shows how DNS tunneling works and lists the commands needed to run this type of attack. That is, you can tunnel IPv4 packets through this DNS channel via the (internal) recursive DNS resolver! Nice approach. ;)

In the end, I’m pointing out how to block these tunnelling attempts with the DNS appliances from Infoblox, and the firewalls from Palo Alto Networks and Fortinet.

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DNS Security @ SharkFest’25 EU

Authentication, Conference Talks, DNS/DNSSEC, Privacy, , , , , , , , ,

I was presenting at the annual “Wireshark Developer and User Conference“, the SharkFest’25 EU, talking about “Securing DNS – Attacks and Defences“. It covered all the buzzwords related to DNS security, such as malware using DNS, DNS spoofing, DNS exfiltration & tunnelling, while defending them with the keywords as DNSSEC, DoH/DoT, feeds & blocklists, and so on.

Quite many techniques. ;) Luckily, the whole session was recorded. So if you’re interested, have a look!

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DNS Packet Capture: DoT, DoH, DoQ, DoH3

DNS/DNSSEC, Privacy, , , , , , , , , ,

While I was working on my presentation about “Secure DNS” for this year’s SharkFest, the Wireshark Developer and User Conference, I recognised that I’m still missing some DNS-related packet captures in the Ultimate PCAP, that is DNS over TLS and DNS over HTTPS. And while working on it with the DNSDiag toolkit (thanks, Babak!), I came across DNS over QUIC and DNS over HTTP/3. 😂 Here we go:

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It was MTU! Zscaler over GRE behind Palo, blocking ICMP Frag Needed

ICMP/ICMPv6, Palo Alto Networks, , , , , , , ,

The other day, I was troubleshooting an issue where users reported that “some websites are working while some are not“. Uh. This is almost the worst scenario to face from a networker’s perspective. It’s way easier if things do or don’t work at all, but not this “some don’t” situation.

The scenario: Using Zscaler for outbound Internet connections, connected via a GRE tunnel from a Palo Alto Networks firewall. TL;DR: If it’s not DNS, it’s MTU. 😂 The “Suppress ICMP Frag Needed” option within the ICMP Drop section of the Zone Protection Profile did what it is meant to do: block “ICMP fragmentation needed” messages. Unfortunately, this killed *some* sessions which had the “Don’t fragment” bit set but exceeded the (lower) MTU of the GRE tunnel.

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Palo vs. PlayStation: How a Security Feature Blocked Our PlayStation Updates

Palo Alto Networks, , , , , ,

For a few weeks, our PlayStation stopped downloading game updates. I figured it was just a temporary issue with the PS4. Since it didn’t affect me directly but only the kids, I didn’t pay much attention at first. I planned to wait for a firmware update from Sony. When such an update eventually came but didn’t solve the issue, I started getting suspicious – especially when I found almost no relevant results online for the official error code, which reads “(HTTP Status Code : 416) (CE-40862-0)”.

After conducting further detailed searches, I finally came across a post in the Palo Alto Networks LIVEcommunity. That definitely caught my attention. If there’s one thing that sets my home network apart from most “normal” households, it’s the fact that I have a Palo Alto firewall running – not your average consumer-grade router. 😂

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Redundant VPN with Failover on a Palo NGFW

Internet Access, IPsec/VPN, Palo Alto Networks, Tutorial/Howto, , , , , ,

This goes out to anyone who uses more than one Site-to-Site VPN tunnel between two locations that are secured by firewalls from Palo Alto Networks. Using two (or even more) VPN tunnels, you need an automatic way to failover the traffic flow from one VPN to the other in case of failures. Here’s how to accomplish that requirement:

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Wireshark Feature Added: Connecting ICMP Errors

ICMP/ICMPv6, Wireshark, , , ,

It’s really just a small thing, but very practical for me: In Wireshark, a feature request I submitted has been implemented. Now, when you click on an ICMP error, the corresponding (original) packet is highlighted.

Previously, clicking on a packet belonging to a flow would show all related packets, including any ICMP errors. However, if you selected an ICMP error packet itself, nothing happened. If you had many ICMP errors from different sessions, you had to go through the cumbersome process of figuring out which sessions they actually belonged to.

Now, you can simply scroll through the packet list as usual and immediately see whether related packets are present — and if so, which ones. Very handy.

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Quizauflösung: Fehlersuche mittels ICMP-Rückmeldungen

ICMP/ICMPv6, , , , , , , ,

Die Fehlersuche in IP-Netzwerken fällt nicht leicht, denn einem Netzwerkschluckauf können viele Ursachen zugrunde liegen. Profi-Admins kennen aber Wege, um das klassische und meist aufwendige Troubleshooting abzukürzen. Beispielsweise kann man Fehlerquellen anhand von ICMP-Rückmeldungen der Netzwerkgeräte eingrenzen, die an einem fehlgeschlagenen IP-Dialog beteiligt sind. Welche Meldungen das sind und wie man sie interpretiert, haben wir hier ausführlich beschrieben.

Am Ende dieses Beitrags haben wir vier Netzwerkanalyse-Aufgaben gestellt. Die Grundlage dafür bildet ein Verkehrsmitschnitt, den man mit dem Analysetool Wireshark öffnet und mit einem Display-Filter siebt. Hier folgen die Antworten zu den Aufgaben.

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ICMP-Meldungen zur Fehlersuche im Netz einspannen

ICMP/ICMPv6, Internet Access, Routing, , , , , , , , , , , ,

Sie sind Admin und Ihr Netz kränkelt. Wo fangen Sie an mit der Fehlersuche? Unser Tipp: Tasten Sie Ihre Netzwerkpatienten mal nach ICMP-Symptomen ab. Viele führen direkt zur Ursache.

Wenn man Netzwerkschluckauf behandeln muss, gilt Wireshark als eines der Lieblingswerkzeuge von Netzwerkadmins. Denn falsch angestöpselten oder fehlkonfigurierten Servern kommt man oft schon anhand eines Netzwerkmitschnitts auf die Spur und erspart sich so den Adminzugriff auf Abteilungsrouter oder -switches. Als behandelnder Admin müssen Sie das aufgefangene Paketkonfetti nur noch mit einem geeigneten Display-Filter sieben, um jene Paketsorte im Kescher zu behalten, die Fehlerhinweise gratis unter Ihre wissenden Augen bringt: die ICMP-Päckchen.

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ICMP ‘Destination Unreachable’ Messages @ SharkFest’24 EU

Conference Talks, ICMP/ICMPv6, Internet Access, , , , , , ,

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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