How To Check Common Wifi Internet Issues

Understanding Internet Addressing

When it comes to the Internet, you may be assigned a Public IPv4 address, such as 60.118.87.127, or a longer and more complex IPv6 address, like 2000:d5f6:25c0:2d1:cc39:670f:61c2:7879. These addresses can be checked at https://test-ipv6.com/, but explaining or identifying them to individuals who are not technically savvy can be error-prone and confusing. Moreover, it lacks historical data, especially for past issues.

Navigating the World Wide Web

When aiming to visit a website, like https://hagenes.io, your computer initially contacts a DNS server to translate the combined host portion (hagenes) and Top Level Domain (io) of the URL into an IP address, such as 140.75.226.215. Furthermore, your computer and web browser share specific type details in all web requests, such as
Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).

Significance of Default Gateways

Typically obtained automatically through DHCP, your default gateway, like 10.130.7.58 (often ending in .1 or .254 depending on the scope size), is where your computer routes all of its traffic. More information on IPv6 connectivity troubleshooting can be found in the detailed guide on how-to-fix-ipv6-connectivity/, and you can verify on Mac or Linux using:

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  10.130.7.58    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:f4e:1b03:89d6:fae7%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): {189.186.248.116, 188.33.28.194}
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 16:64:f8:9f:0c:9e
  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 f8:aa:b5:01:c9:e1
}

Solve Issues with Wired or Wireless Connections

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

Troubleshooting Solutions for Apple macOS / OSX

Regardless of the version of OSX/macOS you are using, be it 10.14.4, 11.0.8, or 12.0.5, there are various troubleshooting tools available. Unfortunately, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes extremely beneficial, especially for teams that are embracing remote work and the Work From Anywhere (WFA) concept.

Useful Built-in Scripts

A very handy tool on OSX/macOS is “sudo wdutil info,” which provides a dump of current wireless related settings to the CLI, 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 only point in time in relation to wireless, similar to wdutil.

To run it in the background and write logs to “/var/tmp/.tar.gz,” use the command “sudo nohup /usr/bin/sysdiagnose -u &.” For an interactive run, use “sudo /usr/bin/sysdiagnose,” but be cautious of the file sizes, which are approximately 300MB.

Possibly Helpful Videos

Video	Title	Channel
	Wireless Packet Captures with Multiple Adapters Yer Yang WLPC Phoenix 2019	Wireless LAN Professionals
	Wi-Fi diagnostics built into MacOS you might not be aware of	Wireless LAN Professionals
	185 Troubleshooting Wi-Fi with Jim Vajda	Wireless LAN Professionals
	The Importance of Broadcast/Multicast Filtering in Wi-Fi HD Arjan Koopen WLPC EU Budapest 2016	Wireless LAN Professionals
	Real World Protocol Analysis Peter Mackenzie WLPC_EU Lisbon 2017	Wireless LAN Professionals

Table 1.0 - Video Help