How To Test Wifi Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a public IPv4 address such as 165.23.237.97 or an IPv6 address like 2000:4763:8e8c:6e86:af3f:fcac:5756:e97c. This information can be verified at https://test-ipv6.com/. However, explaining these addresses, and even mentioning MAC addresses like f6:9f:10:a6:08:30, can be challenging for those not well-versed in technology. Moreover, it fails to provide any historical data, especially when dealing with past issues.
Navigating the Internet
When accessing a website such as https://jakubowski.org, the first step is to connect to a DNS server to convert the host portion (jakubowski) along with the Top Level Domain (org) of the URL into an IP address such as 23.246.190.159. Every web request made by your computer and browser includes its type, for example: 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 typically an address that is automatically configured via DHCP. This default gateway, such as 192.168.35.217 (usually ending in .1 or .254 based on the scope size), is where your computer forwards all its traffic for routing purposes. For IPV6, more information can be found in our in-depth article on how-to-fix-ipv6-connectivity/. To check on Mac or Linux, simply use:
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 192.168.35.217 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 fe80:56fd:8768:2bda:34c6%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): {120.187.10.25, 92.3.138.1}
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 f6:9f:10:a6:08:30
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 26:0b:3d:23:94:b2
}
Fixing Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Options for Apple macOS / OSX
Regardless of whether you are using OSX/macOS versions such as 10.15.8, 11.0.2, or 12.3.9, there are various 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 are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool provides a dump of current wireless related settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool is more comprehensive and can be used to generate a wide range of logs (although most are point-in-time only in relation to wireless, similar to wdutil).
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For interactive usage, run sudo /usr/bin/sysdiagnose, which will give a privacy warning. However, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder. Keep in mind that the file sizes are approximately 300MB.
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