Understand Common Wifi Connectivity
Understanding Internet Addressing
When you use the Internet, you are assigned either a Public IPv4 address, such as 28.4.149.73, or an IPv6 address like 2000:f746:6f59:8fcc:92f8:7bb9:6ed2:7505. You can verify your address by visiting https://test-ipv6.com/. However, explaining or communicating these addresses, along with MAC addresses like b6:06:06:26:20:76, to those who are not tech-savvy can become error-prone and complicated quite quickly. Furthermore, this method doesn’t provide any historical data, especially related to past problems.
Navigating the Internet
Accessing a website like https://schulist.org involves first contacting a DNS server to translate the host portion (schulist) and the Top Level Domain (org) of the URL into an IP address, such as 36.186.236.252. Your computer and browser send their types with each web request, for example, Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).
The Significance of Default Gateways
Usually, your default gateway is an automatically assigned address via DHCP. Your computer is given a default gateway like 192.0.0.136 (usually ending in .1 or .254 depending on the scope size), and this is where your computer sends all of its traffic to be routed onwards. For IPv6, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/, or you can check on Mac or Linux with:
IPv4 Routes and the Host IPv4 Route Table (inc. VPN)
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.0.0.136 UGScg en0 128.0/1 172.18.12.193 UGSc utun3
Note: We are not just looking for the default but also for any VPN that overrides the public v4 address space.
IPv6 Routes and the Host IPv6 Route Table (inc. VPN)
netstat -rn -f inet6 | egrep -i "default|2000::/3"
If you have IPv6 active the above should return at least one route (as per below) via a known interface such as “en0 " on a Mac.
default fe80:c249:d597:65cc:322d%en0 UGcg en0 default fe80::%utun0 UGcIg utun0 default fe80::%utun1 UGcIg utun1 default fe80::%utun2 UGcIg utun2 2000::/3 utun3 USc utun3
Note: We are not just looking for the default but also for any VPN that overrides the public v6 address space.
Debugging DHCP for both IPv4 and IPv6
To get a look at the low level DHCP configuration (Mac/Linux):
ipconfig getpacket en0
...
domain_name_server (ip_mult): {244.246.72.24, 117.209.44.188}
end (none):
...
So, in the above we are not getting IPv6 DNS servers from the DHCPv4 reply but…
ipconfig getv6packet en0
DHCPv6 REPLY (7) Transaction ID 0x80940b Length 76
Options[4] = {
CLIENTID (1) Length 14: DUID LLT HW 1 Time 668691856 Addr b6:06:06:26:20:76
DNS_SERVERS (23) Length 32: 2606:4700:4700::1111, 2001:4860:4860::8844
DOMAIN_LIST (24) Length 0: Invalid
SERVERID (2) Length 10: DUID LL HW 1 Addr 98:94:53:eb:e6:ce
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX Devices
Regardless of whether you are on OSX/macOS 10.15.5, 11.4.3, or 12.2.5, there are various troubleshooting tools available. However, the manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams working remotely and adopting Work From Anywhere (WFA) practices.
Utilizing Built-in Scripts for Assistance
One extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides current wireless settings information to the CLI and can also generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be utilized to generate a wide range of logs, although many are only relevant to the wireless connection, similar to wdutil.
To run this tool in the background and save the logs to /var/tmp/<blah>.tar.gz, use the command: sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, to run it interactively, use the command: sudo /usr/bin/sysdiagnose, which will display a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G or the navigate option. Keep in mind that the file sizes are approximately 300MB.
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