How Do You DiagnOSe Wifi No Access
Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 134.10.99.227 or an IPv6 address like 2000:92b1:8c84:910:95e0:708a:3f8b:2046. You can verify your assigned addresses from https://test-ipv6.com/. However, conveying these addresses to non-technical individuals or even mentioning MAC addresses like c9:50:43:ad:67:f4 can be prone to errors and can become complex. Moreover, this method does not provide historical data, particularly for past issues.
Navigating the Internet
When attempting to access a website such as https://larson.info, the process begins by connecting to a DNS server to convert the host segment (larson) along with the Top Level Domain (info) of the URL to an IP address like 137.250.194.146. Additionally, your computer and browser include its type in all web requests, for example:
<br>Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A```
The Significance of Default Gateways
Typically, your default gateway is an automatically assigned address through DHCP. This default gateway, such as 10.91.192.127 (with commonly ending in .1 or .254 based on the scope size), is where your computer directs all its traffic for further routing. For IPv6, we have an in-depth explanation at how-to-fix-ipv6-connectivity/. To check on Mac or Linux, use the following command:
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 10.91.192.127 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:ad50:a854:b62f:371c%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): {119.125.250.181, 85.15.10.150}
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 c9:50:43:ad:67: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 09:25:6a:f7:42:46
}
Resolving Issues with Wired and Wireless Connections
When transferring data to your router, you may encounter issues with either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting for Apple macOS / OSX Users
Regardless of whether you are using OSX or macOS versions such as 10.15.1, 11.4.5, or 12.1.8, there are various methods for troubleshooting. However, manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that adopt remote work and Work From Anywhere (WFA) policies.
Using Built-in Scripts for Assistance
One useful tool on OSX/macOS is 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 produce a wide range of logs, although many of these are only relevant to a specific point in time, similar to wdutil.
To run it 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 display 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. However, be aware that the file sizes are approximately 300MB.
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