How Can I Test Common Wifi Issues
Understanding Internet Address Assignment
When connecting to the Internet, you may be assigned a Public IPv4 address (e.g. 196.42.162.87) or an IPv6 address (e.g. 2000:2ad3:1909:394c:9cdd:8836:dd47:d7ea). Verifying this assignment can be done through https://test-ipv6.com/. However, conveying these addresses, and even MAC addresses such as 4e:52:d9:bb:ed:41, in non-technical terms can be prone to error and quickly become complex. Additionally, it does not provide any historical data, especially for previous issues.
Navigating the World Wide Web
When accessing a webpage, such as https://waelchi.io, your computer initially contacts a DNS server to translate the host portion (waelchi) combined with the Top Level Domain (io) of the URL into an IP address, such as 163.177.61.42. Furthermore, your computer and browser send their specifications with all web requests, e.g. Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Recognizing the Significance of Default Gateways
The default gateway is usually an automatically configured address obtained via DHCP. This default gateway, such as 10.201.249.241 (typically ending in .1 or .254 based on the scope size), is where your computer forwards all its traffic to be routed onwards. For IPv6, detailed instructions can be found in the deep dive on how-to-fix-ipv6-connectivity/. Alternatively, it can be verified on a Mac or Linux system 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 10.201.249.241 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 fe80:131e:bf09:c5b4:5280%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): {40.145.228.99, 120.14.85.93}
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 4e:52:d9:bb:ed:41
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 cd:a0:cf:7d:f5:a5
}
Resolving Connection Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Addressing Problems on Apple macOS / OSX
Regardless of your version of OSX/macOS - whether it’s 10.15.5, 11.3.2, or 12.0.4 - there are various tools available for troubleshooting. However, these manual procedures and scripts do not provide a set of interconnected values over time. This is where automatic remote troubleshooting becomes particularly useful, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Pre-Installed Scripts That Offer Assistance
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be set up to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (even though there isn’t much interaction), you can execute sudo /usr/bin/sysdiagnose, which will prompt 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. Just be cautious of the file sizes, which are around 300MB or slightly more.
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