How Do You Troubleshoot Common Wifi No Access
Understanding Internet Addressing
When connecting to the Internet, you are assigned either a Public IPv4 address, such as 228.57.120.162, or an IPv6 address like 2000:3d19:8365:6365:cf5b:6dd0:3ac0:e462. One way to verify this is through https://test-ipv6.com/. However, explaining or handling these addresses, as well as MAC addresses like b6:89:27:a4:8f:b1, can be prone to errors and can become complicated, especially for those not well-versed in technology. Moreover, this does not provide any historical data, particularly during past issues.
Navigating the World Wide Web
In order to access a website such as https://labadie-greenfelder.name, your initial step involves contacting a DNS server to convert the host portion (labadie-greenfelder) along with the Top Level Domain (name) of the URL into an IP address like 16.156.142.89. It is worth noting that your computer and browser include identifying information with every web request, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
The default gateway is typically an address that is automatically configured via DHCP. An example of a default gateway is 192.0.0.6 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, comprehensive guidance can be found in our article on how-to-fix-ipv6-connectivity/. It is also possible to verify this on Mac or Linux by 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 192.0.0.6 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 fe80:6761:988b:1680:b981%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): {45.82.188.255, 23.222.160.86}
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 b6:89:27:a4:8f:b1
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 05:fa:53:1b:a5:4e
}
Resolving Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Steps for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.14.1, 11.2.7, or 12.3.7, you have access to a variety of tools 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 crucial, especially for teams that are adopting remote work and the Work From Anywhere (WFA) approach.
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant at a specific point in time regarding wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will issue 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 to specify the path. Keep in mind that the file sizes are approximately 300MB.
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