How Do You Understand Common Wifi Issues
Understanding How Internet Addressing Functions
When connected to the Internet, you are assigned a Public IPv4 address, such as 183.166.199.179, or an IPv6 address, like 2000:b46e:9702:85b:e8c3:aa82:4964:ef79. These addresses can be verified at https://test-ipv6.com/. However, for those who are not tech-savvy, communicating or referencing these addresses, along with MAC addresses like ff:55:4d:fc:6d:de, can be prone to error and become complex. Furthermore, it does not offer any historical data.
Navigating the World Wide Web
When attempting to access a webpage, such as https://osinski.io, the first step involves contacting a DNS server to convert the URL’s host portion (osinski) combined with the Top Level Domain (io) to an IP address, such as 142.7.178.81. With each web request, your computer and browser provide additional details, like Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.
The Significance of Default Gateways
Normally configured through DHCP, your default gateway is the address your computer forwards all of its traffic to, such as 192.168.250.86 (typically ending in .1 or .254 based on the scope size). For IPv6, an in-depth guide is available at how-to-fix-ipv6-connectivity/, but you can verify 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 192.168.250.86 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:f2ff:a6c6:3bdc:690d%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): {48.19.128.212, 9.251.226.192}
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 ff:55:4d:fc:6d:de
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 b3:0c:03:51:68:bb
}
Resolving Wired and Wireless Connection Issues
When it comes to transmitting data to your router, you might encounter issues at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX or macOS version 10.14.3, 11.3.4, or 12.2.2, there are several 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 operate remotely and embrace the Work From Anywhere (WFA) concept.
Useful Built-in Scripts
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose tool, which generates a wide range of logs (although many of the logs are point-in-time related to wireless, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there isn’t much interaction), you can use the commandsudo /usr/bin/sysdiagnose, which will provide 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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