How Can I Troubleshoot Common Wifi Issues
An Overview of Internet Addressing
When connecting to the Internet, you will be assigned either a Public IPv4 address, such as 142.105.117.247, or an IPv6 address like 2000:47fb:d00a:b22f:9e6b:79e1:c368:522f. To verify your assigned address, visit https://test-ipv6.com/. However, communicating these addresses, or MAC addresses like ae:ee:28:8a:ab:a2, can be complex and error-prone for those not well-versed in technology. Additionally, this does not provide any historical data, especially when previous issues occurred.
Navigating the World Wide Web
When accessing a webpage, for example, https://stiedemann-predovic.info, your computer initially contacts a DNS server to translate the host portion (stiedemann-predovic) combined with the Top Level Domain (info) of the URL, to an IP address like 174.205.0.186. Additionally, your computer and browser send their type with all web requests, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
By default, your gateway address is automatically configured via DHCP. This address, such as 172.16.28.115 (though they generally end in .1 or .254 depending on the scope size), is where your computer sends all its traffic to be routed onwards. For IPv6, you can find detailed information in how-to-fix-ipv6-connectivity/. You can also check on Mac or Linux by:
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 172.16.28.115 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:e3a7:54f4:6ec3:5c0f%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): {3.89.243.247, 254.23.17.228}
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 ae:ee:28:8a:ab:a2
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 42:c2:58:58:f0:f2
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you could be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
No matter if you are using OSX/macOS version 10.15.4, 11.2.9, or 12.0.3, there are a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes valuable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the Command Line Interface (CLI) and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to produce a comprehensive set of logs, although much of it is only relevant to wireless settings, like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will generate a privacy warning. If not run in the background, it should open Finder in the correct location, or 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 slightly more.
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