CGNATs and IPv6 over Mobile Broadband
In this lab, we will explore the default behaviour of Mobile broadband with an emphasis on addressing. Before we start looking at the addressing or performance of these networks, lets start with a baseline. Start with the Ubuntu Virtual Machine in the labs.
Contents
Basic Network Baselining
Wired LAN
Open a terminal an type:
ip a
What is your IP address? Is it IPv4, or IPv6? Is it private/public? Confirm your IPv6 predictions here:
https://ipv6test.google.com/
Then go here:
https://whatismyipaddress.com/
Does it correctly resolve your location and IP?
Run a speed test at:
https://www.speedtest.net/
What is your upload and download speed? What latency is reported?
Try pinging:
8.8.8.8
And then:
2001:4860:4860::8888
This is Google DNS server, they are the IPv4 and IPv6 addresses of the same server. Only ping for less than 20 seconds to prevent the university from being blacklisted. What latency do you get? Does it vary a lot?
What is your DNS server? Try a:
cat /etc/resolv.conf
Reflect on the results and compare them with your lab partner.
Eduroam
Connect to eduroam through your Wifi adaptor in Linux, then repeat all of the tests above. Is there any difference? Reflect on the results and compare them with your lab partner.
Open a terminal an type:
ip a
What is your IP address? Is it IPv4, or IPv6? Is it private/public? Confirm your IPv6 predictions here:
https://ipv6test.google.com/
Then go here:
https://whatismyipaddress.com/
Does it correctly resolve your location and IP?
Run a speed test at:
https://www.speedtest.net/
What is your upload and download speed? What latency is reported?
Try pinging:
8.8.8.8
And then:
2001:4860:4860::8888
This is the Google DNS server, they are the IPv4 and IPv6 addresses of the same server. Only ping for less than 20 seconds to prevent the university from being blacklisted. What latency do you get? Does it vary a lot?
What is your DNS server? Try a:
cat /etc/resolv.conf
Reflect on the results and compare them with your lab partner.
Mobile Broadband
Lets start by starting up your personal hotspot on your mobile phone. This should be easy in iOS or Android. Please make sure you use a password. Repeat the steps above.
Open a terminal an type:
ip a
What is your IP address? Is it IPv4, or IPv6? Is it private/public? Confirm your IPv6 predictions here:
https://ipv6test.google.com/
Then go here:
https://whatismyipaddress.com/
Does it correctly resolve your location and IP?
Run a speed test at:
https://www.speedtest.net/
What is your upload and download speed? What latency is reported?
Try pinging:
8.8.8.8
This is Google DNS server. Only ping for less than 20 seconds to prevent the university from being blacklisted. What latency do you get? Does it vary a lot?
What is your DNS server? Try a:
cat /etc/resolv.conf
Reflect on the results and compare them with your lab partner.
IPv6
While still connected to your phone's mobile broadband connection, open a terminal and type:
sudo wireshark
Capture on your WiFi interface do some casual browsing as you capture traffic. Are you using IPv4, IPv6 or both? How do you think your phone works it out.
Fine one of each of the following 3 messages, read about each one and spend 2 minutes on each digging through the headers in wirshark to work out what is going on.
- Neighbor Solicitation
- Neighbor Advertisement
- Router Advertisement
Link Local Addresses
You may be familiar with the idea of a MAC address being a link local address that is only relevant on the LAN. The analogy is not quite correct as MAC addresses work at the data link layer. The closest relative to IPv6 link-local addresses ais the 169.254.0.0/16 subnet. You often see this assigned when you boot up a computer and there is an active network interface but no DHCP server can be found. In IPv6, these link local addresses are always present and are assigned from the block fe80::/10.
Have a look at your link-local address with an:
ip a
Can you identify yours? Now I want you to try to identify the link-local address of your phone and ping it. To do this, look at the neighbor solicitation and neighbour advertisement messages.
You may find that your dns server is your smarthphone.
