How Do You DiagnOSe Common Wifi Issues

Understanding Network Addressing

When using the Internet, you are assigned a unique Public IPv4 address such as 162.129.114.56 or an IPv6 address like 2000:82e6:4762:f7b1:f1b3:4626:2a5a:2f36. These addresses can be verified at https://test-ipv6.com/, and while they are essential for connectivity, conveying and managing them can be complex and error-prone, especially for those less familiar with technical details. Furthermore, historical data is not always readily available.

Navigating Websites

When accessing a website like https://lehner-dickens.info, the first step is to consult a DNS server to translate the URL’s host portion (lehner-dickens) and Top Level Domain (info) into an IP address, such as 132.35.170.102. In every web request, your computer and browser also transmit their type, for example:
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0

The Significance of Default Gateways

The default gateway, usually automatically configured through DHCP, is a crucial component of network connections. Typical default gateway addresses, such as 10.87.156.213 (often ending in .1 or .254), serve as exit points for network traffic. For in-depth instructions on configuring default gateways for IPv6, refer to how-to-fix-ipv6-connectivity/, or use the following commands on Mac or Linux:

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  10.87.156.213    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   fe80:180:63fa:6f70:cc79%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): {179.2.63.111, 142.247.58.111}
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 71:04:15:a6:40:2f
  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 69:66:5a:fe:b1:69
}

Solutions for Connectivity Issues with Wired or Wireless Networks

When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) connection at the physical and data layer.

Troubleshooting Guidance for Mac Operating Systems

Regardless of whether you are using OSX/macOS versions like 10.15.3, 11.1.7, or 12.0.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.

Effective Built-in Tools for Troubleshooting

A useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs related to wireless connectivity, although much of the information is only point-in-time, similar to wdutil.

To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will provide 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 cautious of the file sizes, as they are usually around 300MB.

Possibly Helpful Videos

Video	Title	Channel
	WLAN Troubleshooting David Coleman WLPC US Phoenix 2016	Wireless LAN Professionals
	The Importance of Broadcast/Multicast Filtering in Wi-Fi HD Arjan Koopen WLPC EU Budapest 2016	Wireless LAN Professionals
	Securing the World's Most Dangerous Wi-Fi Network Colin Vallance WLPC Phoenix 2020	Wireless LAN Professionals
	What Problem is UWB Trying to Solve with Stephen Cooper	Wireless LAN Professionals
	185 Troubleshooting Wi-Fi with Jim Vajda	Wireless LAN Professionals

Table 1.0 - Video Help