Troubleshoot Wifi Connectivity
Demystifying Internet Addressing
When using the Internet, you are assigned a unique identifier known as the IP address. It could be a Public IPv4 address, which looks like 207.165.192.5, or an IPv6 address, for example 2000:8588:34ef:fb23:a0ac:b5b1:d263:1c12. These addresses can be verified on https://test-ipv6.com/. However, explaining these addresses to individuals who are not well-versed in technology or even mentioning MAC addresses like ac:6e:c5:14:05:7c can be prone to errors and quickly become complex. Furthermore, this method does not offer any historical data, especially when dealing with previous issues.
Navigating the World Wide Web
When accessing a web page such as https://thompson-green.info, the first step is to contact a DNS server to convert the host portion (thompson-green) along with the Top Level Domain (info) of the URL into an IP address, for example 248.68.209.153. Interestingly, your computer and browser actually transmit their type with all web requests, for instance:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. This default gateway, like 10.139.75.190 (although they frequently end in .1 or .254 depending on the scope size), is where your computer directs all its traffic to be routed further. For those interested in IPv6, we have an extensive explanation available at how-to-fix-ipv6-connectivity/, but you can also verify on Mac or Linux by using the following command:
```bash
command here
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 10.139.75.190 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:c52c:5b4b:d477:5e54%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): {166.35.118.223, 37.199.186.36}
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 ac:6e:c5:14:05:7c
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 8d:19:07:7c:21:33
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using - whether it’s 10.12.6, 11.1.5, or 12.1.5, there are a variety of tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for remote work and Work From Anywhere (WFA) teams.
Useful Built-in Tools for Troubleshooting
One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the following command: sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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