How Can I Test Common Wifi Connectivity
Understanding the Functioning of Internet Addressing
When connecting to the Internet, you are assigned either a Public IPv4 address, such as 176.217.168.161, or an IPv6 address like 2000:9459:2be6:2c8:7fa7:3b0f:e316:7275. You can verify this using https://test-ipv6.com/. However, explaining or communicating these addresses, along with MAC addresses like 83:d6:44:08:b9:20, can be quite challenging for individuals without a technical background. Moreover, this method does not provide any historical data, especially regarding previous problems.
Navigating the World Wide Web
In order to access a website such as https://emmerich.org, your device initially contacts a DNS server to convert the host portion (emmerich) combined with the Top Level Domain (org) of the URL into an IP address, like 123.215.44.122. All web requests from your computer and browser include its type, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Understanding the Significance of Default Gateways
The default gateway is typically an address assigned automatically via DHCP. This could be a default gateway like 192.168.236.143 (usually ending in .1 or .254 based on the scope size), which is where your computer directs all its traffic to be routed onwards. For detailed guidance on IPv6 connectivity, you can refer to how-to-fix-ipv6-connectivity/. Alternatively, you can check on Mac or Linux using:
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 192.168.236.143 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 fd05:38bc:ecc5:72:c1b6:218a:9f61:5e20%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): {102.88.5.163, 242.52.156.163}
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 83:d6:44:08:b9:20
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 dc:5c:0e:d0:7e:4e
}
Resolve Issues with Wired or Wireless Connectivity
When it comes to sending data to your router, you may be using a medium that is either wired or wireless (Wi-Fi) at the physical and data layer.
Tips for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are using, whether it’s 10.11.7, 11.4.5, or 12.0.8, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over a period of time. This is where automated remote troubleshooting becomes valuable, especially for teams that adopt remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One incredibly useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless-related settings to the CLI, and also allows for the generation of specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to generate a comprehensive range of logs (although much of it is only in relation to wireless, similar to wdutil).
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose and heed the privacy warning. When not run in the background, it should open Finder in the correct location, otherwise you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. Keep in mind that the file sizes are approximately 300MB or more.
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