How Can I DiagnOSe Wifi No Access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 139.64.49.97 or an IPv6 address like 2000:e4d7:5c6e:2fef:29:af83:a440:29b1. You can verify this information by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or even referencing MAC addresses like bc:71:af:2e:67:bb can be prone to errors and become complex. Moreover, this method does not provide any historical data, particularly for past issues.
Navigating the World Wide Web
Accessing a website like https://shanahan.io involves initially accessing a DNS server to convert the host section (shanahan) combined with the Top Level Domain (io) of the URL into an IP address like 176.255.242.47. Your computer and browser also include its type in 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 through DHCP. This results in a default gateway like 192.168.106.83 (often ending in .1 or .254, based on the scope size), which is the point where your computer sends all its traffic to be routed onward. For IPv6 troubleshooting, you can refer to our article how-to-fix-ipv6-connectivity/ and on Mac or Linux systems, you can verify this with:
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 192.168.106.83 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:ee24:e3bd:f398:133a%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): {32.244.29.132, 232.24.144.200}
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 bc:71:af:2e:67:bb
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 af:ba:66:50:f0:b8
}
Fixing Connection Issues for Wired and Wireless Networks
When transferring data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are running - whether it’s 10.15.4, 11.2.4, or 12.0.7 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very handy tool on OSX/macOS is “sudo wdutil info,” which provides a dump of current wireless-related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the “sysdiagnose” tool can be used to generate a variety of logs, although much of it is only useful at a specific point in time in relation to wireless, similar to wdutil.
To run “sudo nohup /usr/bin/sysdiagnose -u &” in the background and write logs to “/var/tmp/
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