How Can I Fix Common Wifi Issues

Understanding the Functionality of Internet Addressing

When using the Internet, individuals may be assigned a Public IPv4 address, such as 69.213.88.130, or an IPv6 address like 2000:e7a3:469c:825d:c12:4fff:6800:2097. This assignment can be verified at https://test-ipv6.com/. However, expressing and relaying these addresses, as well as MAC addresses like 35:0f:d5:de:51:87, can be prone to error and complicated, particularly for those not well-versed in technology. Additionally, it does not provide any historical data, especially in instances where previous issues arose.

Navigating Web Access

To access a webpage, such as https://gutmann-schiller.name, one must first contact a DNS server in order to convert the host portion (gutmann-schiller) combined with the Top Level Domain (name) of the URL to an IP address, like 247.98.45.170. Each time a computer and browser make web requests, they send specific type information, such as
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

Typically, the default gateway is an automatically assigned address via DHCP. An individual’s default gateway, such as 172.18.155.56 (typically ending in .1 or .254 based on the scope size), is where their computer sends all traffic to be routed onwards. For IPv6, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/, and can also be verified on Mac or Linux using 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  172.18.155.56    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   fe80:426b:13c1:9539:bb28%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): {26.177.164.106, 163.93.88.180}
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 35:0f:d5:de:51:87
  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 5e:f8:05:eb:81:64
}

Resolving Wired and Wireless Issues

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

Troubleshooting Tips for Apple macOS / OSX

No matter which version of OSX/macOS you’re using, whether it’s 10.14.1, 11.1.2, or 12.0.2, there are various tools available for troubleshooting. However, these manual actions and scripts don’t provide a series of correlated values over time, making automated remote troubleshooting essential, particularly for teams that embrace remote work and Work From Anywhere (WFA).

Useful Built-in Scripts

One useful tool on OSX/macOS is sudo wdutil info, 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 can be used to generate a wide range of logs, although many are only relevant at a specific time in relation to wireless, similar to wdutil.

Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use
sudo /usr/bin/sysdiagnose which will prompt a privacy warning. If not running in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are about 300MB more or less.

Possibly Helpful Videos

Video	Title	Channel
	Troubleshooting in Higher Ed Stefan Kronawithleitner WLPC Prague 2023	Wireless LAN Professionals
	WLAN Troubleshooting David Coleman WLPC US Phoenix 2016	Wireless LAN Professionals
	Bad Wi-Fi? Are you SURE it's a wireless problem? Here's how to find out	Wireless LAN Professionals
	TIP OpenWifi Demo Network Setup for WLPC Drew Lentz WLPC Prague 2022	Wireless LAN Professionals
	What Problem is UWB Trying to Solve with Stephen Cooper	Wireless LAN Professionals

Table 1.0 - Video Help