How Do You Test Wifi Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 45.165.92.227 or an IPv6 address like 2000:5d7d:2cb0:3419:5c7e:d7bf:24c2:a44. You can verify your address at https://test-ipv6.com/. Describing or identifying these addresses, or MAC addresses like c9:52:91:d1:8f:19 to those not knowledgeable in technology can be prone to errors and become complex. Moreover, this method does not provide historical data, particularly from past issues.
Navigating the World Wide Web
When accessing a website such as https://schroeder.com, you first connect to a DNS server to convert the host portion (schroeder) combined with the Top Level Domain (com) of the URL to an IP address like 202.134.17.236. Your computer and browser also provide their specifications with every web request e.g. Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
The Significance of Default Gateways
The default gateway is usually an automatically assigned address through DHCP, such as 192.168.188.3 (commonly ending in .1 or .254 based on scope size). This is the point where your computer directs all its traffic to be routed forward. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/, or you can verify 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 192.168.188.3 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:abd1:d89e:bb7:6bcd%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): {230.216.93.243, 117.108.133.7}
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 c9:52:91:d1:8f:19
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 9c:e0:45:cb:33:c6
}
Resolve Issues with Wired or Wireless Connectivity
When it comes to transmitting data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Actions to Take on Apple macOS / OSX Systems
Regardless of the version of OSX or macOS you are running, whether it’s 10.15.5, 11.3.3, or 12.2.4, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are transitioning to remote work and embracing Work From Anywhere (WFA).
Useful Built-in Tools for Troubleshooting
A very effective tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can 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 is only relevant to wireless at a specific point in time, much like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (even though there isn’t much interaction), you can use sudo /usr/bin/sysdiagnose, which will issue 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. However, be cautious of the file sizes, which are approximately 300MB or so.
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