How Do You Test Common Wifi Connectivity
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 202.93.186.224, or an IPv6 address, like 2000:468a:3ec4:246f:35d6:e565:8012:a4be. You can verify these addresses at https://test-ipv6.com/. However, conveying these addresses or MAC addresses, such as d5:2d:16:53:26:6c, can be error-prone and complex for non-technical individuals. Moreover, this information does not offer historical data, especially concerning past issues.
Navigating the World Wide Web
When accessing a website, like https://rowe-stanton.io, you first connect to a DNS server to convert the host portion (rowe-stanton) combined with the Top Level Domain (io) of the URL into an IP address, such as 247.68.236.37. Additionally, your computer and browser share their information with all web requests, 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 Gateway
The default gateway is typically an automatically configured address obtained through DHCP. The default gateway, like 172.20.85.228 (often ending in .1 or .254 depending on the scope size), is where your computer forwards all its traffic for routing. For IPv6, detailed instructions are available in our article on how-to-fix-ipv6-connectivity/. Additionally, you can verify this information 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 172.20.85.228 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:b59:6f5e:4352:3789%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): {219.221.109.143, 74.170.201.157}
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 d5:2d:16:53:26:6c
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 4e:02:dc:8e:a3:7a
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may use a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX Devices
Regardless of whether you are using OSX or macOS version 10.13.9, 11.0.3, or 12.1.2, there are various tools available for solving connectivity issues. However, these tools do not provide a comprehensive set of correlated values over time, which is where automated remote troubleshooting becomes valuable, especially for remote teams and those practicing Work From Anywhere (WFA).
Effective Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides current wireless settings dump 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 point-in-time data, similar to wdutil.
To run the sysdiagnose tool in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. To run it interactively, use the command sudo /usr/bin/sysdiagnose, which will provide a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp manually. Keep in mind that the file sizes are around 300MB.
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