How To Test Common Wifi Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 223.98.220.179, or an IPv6 address, such as 2000:73a1:82cd:818b:93eb:8b3f:4af8:deae. You can verify this information at https://test-ipv6.com/. However, for those who are not familiar with technical terminology, conveying and working with these addresses, as well as MAC addresses, like 7f:45:be:ad:36:b5, can quickly become error-prone and complex. Furthermore, this process does not provide any historical information, especially when previous issues occurred.
Navigating the World Wide Web
In order to access a specific web page, such as https://lockman.name, you first need to contact a DNS server to convert the host portion (lockman) combined with the Top Level Domain (name) of the URL into an IP address, like 192.197.17.219. Whenever you make a web request, your computer and browser communicate your specifications, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is typically an address that is automatically configured through DHCP. This gateway, such as 172.29.63.209 (often using .1 or .254 at the end, depending on the scope size), is where your computer directs all of its traffic to be routed further. For IPv6, there is a detailed explanation available at how-to-fix-ipv6-connectivity/, but on Mac or Linux, you can verify 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 172.29.63.209 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:b2f7:ec0d:6e6:6284%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): {17.157.88.250, 132.209.175.117}
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 7f:45:be:ad:36:b5
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 fc:0b:13:56:fa:58
}
Resolve Issues with Wired and Wireless Connections
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Dealing with Apple macOS / OSX Problems
Regardless of which version of OSX/macOS you are running, whether it’s 10.13.2, 11.1.6, or 12.1.4, there are various troubleshooting tools available. 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 embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A helpful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless settings and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a variety of logs, although much of it is only point-in-time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /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 or use Finder with Cmd+Shift+G to point Finder to the path. Keep in mind that the file size is approximately 300MB.
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