Troubleshoot Wifi No Access
Understanding the Functioning of Internet Addressing
When using the Internet, individuals may obtain a Public IPv4 address, such as 116.81.6.184, or an IPv6 address like 2000:964d:ff43:8224:4631:605f:a388:1be5. This information can be verified through https://test-ipv6.com/. However, communicating these addresses, or even mentioning MAC addresses like b2:d1:24:97:de:48, can be prone to errors and become complex, especially for those with limited technical knowledge. Moreover, this method does not provide any historical information, particularly when dealing with past issues.
Navigating the World Wide Web
In order to access a webpage, such as https://kling.biz, individuals initially connect to a DNS server to convert the host portion (kling) combined with the Top Level Domain (biz) of the URL to an IP address, for instance, 151.13.2.34. Each web request from a computer and browser includes the specified 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
Significance of Default Gateways
The default gateway is typically an automatically assigned address via DHCP, such as 192.0.0.194 (although they generally end in .1 or .254 based on the scope size), and serves as the destination for routing all traffic from a computer. For IPv6, detailed instructions can be found in the article how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux, users can verify this information 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 192.0.0.194 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:eb46:6577:ce56:6cd0%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): {66.41.42.156, 151.60.214.135}
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 b2:d1:24:97:de:48
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 16:0d:d3:0e:96:96
}
Resolving Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS version 10.15.9, 11.0.5, or 12.1.6, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time, making automated remote troubleshooting crucial, particularly for teams practicing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A valuable tool for OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool offers a comprehensive range of logs, although many are only relevant at a specific point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. Alternatively, for an interactive run (although there is minimal interaction), you can use the command sudo /usr/bin/sysdiagnose, which will prompt 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 or through the path. Keep in mind that the file sizes are approximately 300MB.
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