How To Troubleshoot Wifi Connectivity

Understanding Internet Addressing

When using the Internet, you are assigned a Public IPv4 address, such as 13.45.47.100, or an IPv6 address, such as 2000:296f:7959:e0ae:d059:a569:ba1a:d104. You can verify your address at https://test-ipv6.com/. However, explaining and communicating these addresses, as well as MAC addresses like bf:8a:d8:24:e4:46, can become complex, especially for those not well-versed in technology. Moreover, this method does not provide any historical data, particularly when dealing with previous issues.

Navigating the World Wide Web

When accessing a website, such as https://klein-mayert.org, your computer first contacts a DNS server to convert the host portion (klein-mayert) along with the Top Level Domain (org) of the URL into an IP address, like 230.72.158.124. Furthermore, your computer and browser transmit their specifications with every web request, for example:
Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16

The Significance of Default Gateways

Your default gateway is typically an address that is automatically configured via DHCP and is often assigned a number ending in .1 or .254, depending on the scope size, such as 10.130.125.171. This is the location where your computer directs all of its traffic for routing. To learn more about IPv6 connectivity, you can find a comprehensive guide at how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux systems, you can verify default gateways with the following commands:

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  10.130.125.171    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:a68:757f:e758:f5a0%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): {101.22.25.9, 231.38.222.36}
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 bf:8a:d8:24:e4:46
  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 95:c9:df:cf:7a:55
}

Troubleshooting Connectivity Issues

When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.

Troubleshooting Techniques for Apple macOS / OSX

Regardless of whether you are running 10.11.5, 11.0.8, or 12.1.1, there are various tools available for troubleshooting on OSX/macOS. 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 practice remote work and Work From Anywhere (WFA).

Useful Built-in Scripts

A very useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool offers a more comprehensive option to generate a wide range of logs, although many are only point-in-time related to wireless, 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 sudo /usr/bin/sysdiagnose and it will give a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. Keep in mind that the file sizes are approximately 300MB.

Possibly Helpful Videos

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	Wireless Adjuster Certification - Do You Need It?	Wireless LAN Professionals
	What Problem is UWB Trying to Solve with Stephen Cooper	Wireless LAN Professionals
	IEEE 802 11kvr Perry Correll WLPC Phoenix 2019	Wireless LAN Professionals
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Table 1.0 - Video Help