How Do You Test Wifi Issues
A Guide to Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 77.174.28.194, or an IPv6 address, like 2000:e030:8fcc:6b5:4adc:a743:4ca7:7291. Verification can be done at https://test-ipv6.com/. However, it can be challenging for individuals who are not tech-savvy to communicate these addresses or even MAC addresses like 0c:51:9a:7e:53:87, and complications arise quickly. Additionally, no historical data is provided, especially for previous issues.
Navigating the World Wide Web
Accessing a webpage, such as https://okon.name, involves initially accessing a DNS server to translate the host portion (okon) along with the Top Level Domain (name) of the URL into an IP address, like 49.147.220.29. Every web request from your computer and browser includes its type, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
The Significance of Default Gateways
A default gateway, usually configured automatically via DHCP, is assigned to you, such as 192.168.215.128 (commonly ending in .1 or .254 depending on the scope size). This is where your computer routes all its traffic. For IPv6, a detailed explanation can be found in how-to-fix-ipv6-connectivity/, but you can verify on Mac or Linux with:
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 192.168.215.128 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 fe80:9687:5390:6934:a76d%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): {95.127.164.169, 124.191.193.227}
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 0c:51:9a:7e:53:87
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 3f:cc:f4:2f:ae:cf
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, the choice between using a wired or wireless (Wi-Fi) medium at the physical and data layer can impact the troubleshooting process.
Effective Steps for Apple macOS / OSX Users
Whether you are running OSX/macOS versions such as 10.11.6, 11.4.6, or 12.0.2, there are various troubleshooting tools available. However, these tools and manual actions may not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are immersed in remote work and Work From Anywhere (WFA) practices.
Leveraging Useful Built-in Scripts
A valuable tool for troubleshooting on OSX/macOS is the sudo wdutil info, which provides a detailed dump of current wireless settings through the CLI, and can also generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although many of these logs are only relevant to the wireless aspect, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. For an interactive experience (despite minimal interaction), running sudo /usr/bin/sysdiagnose will prompt a privacy warning and should open Finder in the correct location, allowing users to navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. It’s important to note that the file sizes are generally around 300MB.
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