How To Check Wifi Connectivity
Demystifying Internet Addressing
In the realm of the Internet, individuals are assigned unique identifying addresses such as the Public IPv4 address 102.79.6.28 or the IPv6 address 2000:d8b8:3860:d696:4fed:b1a9:ff0c:606. An efficient way to verify this information is to visit https://test-ipv6.com/. Nevertheless, the challenge arises when attempting to articulate these addresses, or even recite MAC addresses like 0b:2b:ea:31:ac:a8, especially for those who are not technologically inclined. This can lead to errors and a rapid increase in complexity. Moreover, this practice does not provide historical data, particularly when referring to past occurrences of issues.
Navigating the World Wide Web
Accessing a specific website such as https://vandervort-pfeffer.net first requires a query to a DNS server, which translates the host portion (vandervort-pfeffer) in combination with the corresponding Top Level Domain (net) of the URL, into an IP address like 30.168.255.22. Notably, every web request initiated by your computer and browser includes data about their type, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
Typically, your default gateway is automatically assigned through DHCP and takes the form of an address such as 10.37.143.29 (usually ending in .1 or .254 depending on the scope size). This is where your computer directs all of its traffic to be routed further. If you are interested in more detailed information about this process for IPv6, a comprehensive guide can be found in our blog post titled how-to-fix-ipv6-connectivity/. Additionally, you can use the following command on Mac or Linux to check for your default gateway:
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 10.37.143.29 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:c7cc:b6a3:5cc3:b9fc%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): {8.212.42.172, 149.43.211.175}
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 0b:2b:ea:31:ac:a8
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 00:a1:29:3f:88:07
}
Fixing Connectivity Issues
When it comes to sending data to your router, you may encounter connectivity issues at the physical and data layer, whether you’re using a wired or wireless (Wi-Fi) medium.
Troubleshooting on Apple macOS / OSX Devices
Regardless of the version of OSX/macOS you’re using - be it 10.15.9, 11.1.2, or 12.3.3 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, making automated remote troubleshooting particularly valuable for teams that embrace remote work and Work From Anywhere (WFA).
Using Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which 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 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, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, for an interactive experience, use sudo /usr/bin/sysdiagnose, which will display a privacy warning. When run not in the background, it should open Finder in the correct location, or you can navigate to /var/tmp and beware of file sizes of around 300MB.
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