How To Understand Common Wifi Issues
Understanding Internet Addressing Mechanism
When using the Internet, you are assigned a Public IPv4 address such as 115.65.69.175 or an IPv6 address like 2000:a4ae:e430:55b3:3472:45ef:d6:8a80. You can verify this information at https://test-ipv6.com/. However, communicating these addresses or MAC addresses like 1d:7b:3f:bd:e3:22 can be prone to errors and can become intricate for individuals who are not well-versed in technology. Furthermore, this information does not provide any historical data, especially about past issues.
Navigating Through the Internet
When accessing a web page like https://howe.biz, the process begins with contacting a DNS server to convert the host portion (howe) combined with the Top Level Domain (biz) of the URL into an IP address like 200.248.60.108. Your computer and browser indicate its type with every web request, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
Your default gateway is typically an automatically assigned address via DHCP, such as 192.168.206.120 (although they typically end in .1 or .254, depending on the scope size), and this is where your computer sends all traffic to be routed onwards. For a detailed examination of IPv6 connectivity, refer to how-to-fix-ipv6-connectivity/. You can also check 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 192.168.206.120 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 fe80:6f7e:fa20:ff77:a56d%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): {87.20.207.227, 245.240.193.71}
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 1d:7b:3f:bd:e3:22
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 de:6d:17:15:e3:57
}
Resolving Issues with Wired and Wireless Connections
When it comes to transferring data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS versions such as 10.13.8, 11.2.9, or 12.1.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide correlated values over time, which is where automated remote troubleshooting becomes invaluable, especially for teams embracing remote work and the Work From Anywhere (WFA) approach.
Useful Built-in Scripts
One helpful tool for OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless 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 relates to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For interactive use, run sudo /usr/bin/sysdiagnose, which 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 using Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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