How To Troubleshoot Common Wifi Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 1.145.105.30 or an IPv6 address like 2000:f61e:16b1:f9c1:8e71:91ee:e3a0:1a21. These addresses can be verified on https://test-ipv6.com/. However, explaining these addresses, or even recalling MAC addresses like 82:b9:c6:e1:71:e1, can be prone to errors and can become complex rather quickly. Moreover, this method does not provide any historical data, particularly from previous occurrences of problems.
Navigating the World Wide Web
To access a web page such as https://farrell-kuhic.org, you initially contact a DNS server to convert the host portion (farrell-kuhic) combined with the Top Level Domain (org) of the URL, into an IP address like 71.160.56.51. Your computer and browser sends its type along with all web requests, 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
Your default gateway is typically an automatically configured address through DHCP. You are provided with a default gateway like 192.0.0.37 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed further. For IPv6, you can explore in detail on how-to-fix-ipv6-connectivity/, and you can verify on Mac or Linux 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 192.0.0.37 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:ddd:6a12:9fe6:e267%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): {76.114.24.40, 127.248.15.150}
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 82:b9:c6:e1:71:e1
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 8c:81:2a:60:81:02
}
Solutions for Wired and Wireless Network 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.
Steps to Take for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you have, whether it’s 10.15.7, 11.1.7, or 12.2.5, there are various troubleshooting tools available. However, these manual actions and scripts don’t provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless related settings 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 related to wireless settings at a specific point in time, similar to wdutil).
To run it in the background and save logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run, you can use sudo /usr/bin/sysdiagnose, which will give a privacy warning and open Finder in the correct location or navigate to ```/var/tmp``. Keep in mind that the file sizes are about 300MB more or less.
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