How Can I DiagnOSe Wifi Internet Issues

Working Mechanism of Internet Addressing

When using the Internet, you are assigned a Public IPv4 address, such as 238.10.21.190, or an IPv6 address, like 2000:fec1:8b25:c8b1:6d96:e770:3c1b:e0a. You can verify this information at https://test-ipv6.com/. However, for those who are not well-versed in technology, conveying these addresses or recalling MAC addresses, such as 93:17:e6:bd:df:38, can be prone to errors and quickly become complex. Moreover, this does not provide any historical data, especially when dealing with past issues.

Navigating the World Wide Web

In order to access a website, like https://ryan.name, your device first reaches out to a DNS server to convert the host portion (ryan) along with the Top Level Domain (name) of the URL to an IP address, such as 5.26.252.197. Furthermore, your computer and browser include its type in all web requests, for example:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko

The Significance of Default Gateways

The default gateway is typically an address that is automatically configured via DHCP. It usually resembles a default gateway like 10.62.185.77 (commonly ending in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed onwards. For IPv6, there is an in-depth explanation in how-to-fix-ipv6-connectivity/; however, you can verify this on Mac or Linux with 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  10.62.185.77    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:a724:2b36:1e28:63d4%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): {253.14.54.252, 45.233.144.126}
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 93:17:e6:bd:df:38
  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 f9:3e:51:36:f1:d2
}

Fixing Issues with Wired and Wireless Connections

Whether you are using a wired or wireless (Wi-Fi) medium to send data to your router, troubleshooting at the physical and data layer is crucial.

Tips for Resolving Problems on Apple’s macOS / OSX

No matter which version of OSX/macOS you are currently running - whether it’s 10.14.1, 11.5.8, or 12.0.3 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are engaged in remote work and Work From Anywhere (WFA).

Using Built-in Scripts to Aid in Troubleshooting

One extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless related settings and can be set up to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless settings at a specific point in time, similar to wdutil.

Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (even though there is not much interaction), you can run
sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. If 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 to point Finder to the path. Keep in mind that the file sizes will be around 300MB or so.

Possibly Helpful Videos

Video	Title	Channel
	Automated Root Cause Analysis in Wireless Networks Karan Gupta	Wireless LAN Professionals
	Securing the World's Most Dangerous Wi-Fi Network Colin Vallance WLPC Phoenix 2020	Wireless LAN Professionals
	TIP OpenWifi Demo Network Setup for WLPC Drew Lentz WLPC Prague 2022	Wireless LAN Professionals
	WiFiShark Fu Eddie Forero WLPC Phoenix 2019	Wireless LAN Professionals
	Wireless Adjuster Certification - Do You Need It?	Wireless LAN Professionals

Table 1.0 - Video Help