How To Troubleshoot Wifi No Access
Explanation of Internet Addressing
When using the Internet, we are assigned a Public IPv4 address (like 156.142.81.99) or an IPv6 address (like 2000:a00:ee91:c17:7ef9:5ed4:6ba6:9cb5). The process of communicating these addresses, or MAC addresses (like 25:52:dd:2e:83:f4), can be complicated, especially for those who are not well-versed in technology. Additionally, this method does not provide any historical data.
Process of Accessing the Internet
Accessing websites, such as https://stamm-mosciski.co, involves initially accessing a DNS server to translate the URL, consisting of the host portion (stamm-mosciski) and the Top Level Domain (co), into an IP address (like 22.102.35.174). Furthermore, each web request sent from your computer and browser includes the type of browser being used, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
The default gateway, typically obtained through DHCP, is an automatically configured address (like 192.0.0.142) where your computer sends all its traffic to be routed onwards. For IPv6, a more detailed guide can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can check the default gateway using the following method:
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 192.0.0.142 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 fe80:2a43:ed5d:5b8f:75e%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): {85.154.39.110, 147.163.69.230}
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 25:52:dd:2e:83:f4
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 e5:6d:3e:4a:db:0a
}
Analyzing and Resolving Connectivity Issues
In the realm of physical and data layer connectivity, users may utilize either a wired or wireless (Wi-Fi) medium to transmit data to their router.
Steps to Follow for Apple’s macOS / OSX Platform
Irrespective of the version of OSX/macOS being used – be it 10.11.6, 11.6.3, or 12.2.1 – there exists a plethora of tools available for diagnosing connectivity issues. Regrettably, these manual interventions and scripts fail to provide a comprehensive set of interconnected values over a period. This is where the significance of automated remote troubleshooting comes into play, especially for teams advocating remote work and Work From Anywhere (WFA).
Pre-Installed Scripts for Troubleshooting
An immensely useful tool on OSX/macOS is the sudo wdutil info, which offers a detailed report of current wireless settings through the CLI. Furthermore, it can be configured to produce specific logs for troubleshooting purposes. Moreover, the sysdiagnose tool, although mainly offering point-in-time logs related to wireless like wdutil, provides a more extensive range of logs.
By executing sudo nohup /usr/bin/sysdiagnose -u &, the tool can be run in the background, while simultaneously writing logs to /var/tmp/<blah>.tar.gz. If there is a preference for an interactive (although minimal interaction) setup, running sudo /usr/bin/sysdiagnose will trigger a privacy warning. Not running it in the background should prompt Finder to open in the correct location, or users can manually navigate to /var/tmp using Finder or employ Cmd+Shift+G to guide Finder to the specified path. It is advisable to be mindful of the file sizes, which typically hover around 300MB.
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