The other day I wanted to verify whether a service running on my Linux server was listening on IPv6 as well as IPv4. It turned out that it wasn’t that easy to answer – if at all.
Continue reading Services listening on IPv6 and IPv4 (or maybe not?)
Category Archives: IPv6
UK IPv6 Council Spring 2020: Incorrect Working IPv6 Clients & Networks
I did a short presentation at the spring 2020 roundtable of the UK IPv6 Council. The talk was about a case study I did with my NTP server listed in the NTP Pool project: For 66 days I captured all NTP requests for IPv6 and legacy IP while analyzing the returning ICMPv6/ICMPv4 error messages. (A much longer period than my initial capture for 24 hours.) Following are my presentation slides along with the results.
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SharkFest’19 EUROPE: IPv6 Crash Course
I gave a session about IPv6 at SharkFest’19 EUROPE, the annual Wireshark developer and user community conference, named “IPv6 Crash Course: Understanding IPv6 as seen on the wire“. The talk is about the IPv6 basics, which are: IPv6 addresses & address assignment, link-layer address resolution, and ICMPv6. Tips for using Wireshark coloring rules and display filters round things up.
As I have not yet published the slides, here they are. Unfortunately, we were not able to record the session due to technical problems. Neither the video nor the audio. ;( Hence, here are only mere slides.
I Love IPv6 Addressing!
Probably the biggest prejudice when it comes to IPv6 is: “I don’t like those long addresses – they are hard to remember.” While this seems to be obvious due to the length and hexadecimal presentation of v6 addresses, it is NOT true. In the end, you’ll love IPv6 addresses in your own networks. This is why – summed up in one poster:
Incorrect Working IPv6 NTP Clients/Networks
During my analysis of NTP and its traffic to my NTP servers listed in the NTP Pool Project I discovered many ICMP error messages coming back to my servers such as port unreachables, address unreachables, time exceeded or administratively prohibited. Strange. In summary, more than 3 % of IPv6-enabled NTP clients failed in getting answers from my servers. Let’s have a closer look:
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6in4 Traffic Capture
Since my last blogposts covered many 6in4 IPv6 tunnel setups (1, 2, 3) I took a packet capture of some tunneled IPv6 sessions to get an idea how these packets look like on the wire. Feel free to download this small pcap and to have a look at it by yourself.
A couple of spontaneous challenges from the pcap round things up. ;)
Juniper ScreenOS with a 6in4 Tunnel
Yes, I know I know, the Juniper ScreenOS devices are Out-of-Everything (OoE), but I am still using them for a couple of labs. They simply work as a router and VPN gateway as well as a port-based firewall. Perfect for labs.
For some reasons I had another lab without native IPv6 Internet. Hence I used the IPv6 Tunnel Broker one more time. Quite easy with the SSGs, since HE offers a sample config. But even through the GUI it’s just a few steps:
Workaround for Not Using a Palo Alto with a 6in4 Tunnel
Of course, you should use dual-stack networks for almost everything on the Internet. Or even better: IPv6-only with DNS64/NAT64 and so on. ;) Unfortunately, still not every site has native IPv6 support. However, we can simply use the IPv6 Tunnel Broker from Hurricane Electric to overcome this time-based issue.
Well, wait… Not when using a Palo Alto Networks firewall which lacks 6in4 tunnel support. Sigh. Here’s my workaround:
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Using a FortiGate with a 6in4 Tunnel
For some reason, I am currently using a FortiGate on a location that has no native IPv6 support. Uh, I don’t want to talk about that. ;) However, at least the FortiGate firewalls are capable of 6in4 tunnels. Hence I am using the IPv6 Tunnel Broker from Hurricane Electric again. Quite easy so far.
But note, as always: Though FortiGate supports these IPv6 features such as a 6in4 tunnel or stateful/-less DHCPv6 server, those features are NOT stable or well designed at all. I had many bugs and outages during my last years. Having “NAT enabled” on every new IPv6 policy is ridiculous. Furthermore, having independent security policies for legacy IP and IPv6 is obviously a really bad design. One single policy responsible for both Internet protocols is a MUST. Anyway, let’s look at the 6in4 tunnel:
Using Case Sensitive IPv6 Addressing on a Palo Alto
IPv6 brings us enough addresses until the end of the world. Really? Well… No. There was an interesting talk at RIPE77 called “The Art of Running Out of IPv6 Addresses” by Benedikt Stockebrand that concludes that we will run out of IPv6 addresses some day.
Luckily Palo Alto Networks has already added one feature to expand the IPv6 address space by making them case sensitive. That is: you can now differentiate between upper and lower case values “a..f” and “A..F”. Instead of 16 different hexadecimal values you now have 22 which increases the IPv6 space from 
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Packet Capture: Network Time Protocol (NTP)
What’s the first step in a networker’s life if he wants to work with an unknown protocol: he captures and wiresharks it. ;) Following is a downloadable pcap in which I am showing the most common NTP packets such as basic client-server messages, as well as control and authenticated packets. I am also showing how to analyze the delta time with Wireshark, that is: how long an NTP server needs to respond to a request.
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Trying to change an IPv6 Link-Local Address on a FortiGate
I got an email where someone asked whether I know how to change the link-local IPv6 addresses on a FortiGate similar to any other network/firewall devices. He could not find anything about this on the Fortinet documentation nor on Google.
Well, I could not find anything either. What’s up? It’s not new to me that you cannot really configure IPv6 on the FortiGate GUI, but even on the CLI I couldn’t find anything about changing this link-local IPv6 address from the default EUI-64 based one to a manually assigned one. Hence I opened a ticket at Fortinet. It turned out that you cannot *change* this address at all, but that you must *add* another LL address which will be used for the router advertisements (RA) after a reboot (!) of the firewall. Stupid design!
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SharkFest’18 Europe: Crash Course: IPv6 and Network Protocols
I did a session at SharkFest’18 Europe in Vienna with the title of “Crash Course: IPv6 and Network Protocols“. Since the presentation slides + audio were recorded you can listen to the talk, too. Here are some notes about the motivation for this session as well as feedback from the attendees.
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My CCNP TSHOOT Lab: The Overall Picture
During the last few weeks I published a couple of blogposts concerning routing protocols such as BGP, OSPFv3, and EIGRP. (Use the “Cisco Router” tag on my blog to list all of them.) They are all part of my current Cisco lab that I am using for my CCNP TSHOOT exam preparation. While I depicted only the details of the routing protocols in those blogposts, I am showing my overall lab with all of its Cisco IOS configs here. Just to have the complete picture. There are a couple of not-yet-blogged configs such as VRRP, GLBP, NTP authentication, embedded event manager (EEM), or route-maps and distribute/prefix lists though.
EIGRP Capture
And again: Here comes a pcapng capture taken for the dynamic routing protocol EIGRP. If you want to dig into EIGRP messages, download the trace file and browse around it with Wireshark. Since I used both Internet Protocols (IPv6 and legacy IP), MD5 authentication, route redistribution, etc., you can find many different messages in it.