How To Understand Wifi Connectivity
Understanding the Functionality of Internet Addressing
When connecting to the Internet, you are assigned either a Public IPv4 address such as 5.143.19.214 or an IPv6 address like 2000:9056:b050:e571:f006:62ef:8c25:641f. These can be verified at https://test-ipv6.com/. However, communicating these addresses to individuals who are not technically inclined, or relaying MAC addresses like 93:0a:13:be:1c:d5, can be prone to errors and can become complex rather quickly. Additionally, this method lacks historical data, especially pertaining to past incidents.
Navigating the World Wide Web
Accessing a web page such as https://strosin-grimes.co initially involves connecting to a DNS server in order to translate the host portion (strosin-grimes) combined with the Top Level Domain (co) of the URL into an IP address such as 28.66.221.81. With every web request, your computer and browser sends its type e.g. Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).
The Significance of Default Gateways
Usually, your default gateway is automatically configured through DHCP and is assigned an address such as 10.99.219.202 (typically ending with .1 or .254 based on the scope size). This is the designated point to which your computer sends all of its traffic to be routed onwards. For detailed information on IPv6, an in-depth analysis can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux systems, this can be verified by using the following command:
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 10.99.219.202 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 fe80:1347:e5be:18c6:ef11%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): {14.167.226.179, 230.249.198.59}
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 93:0a:13:be:1c:d5
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 33:7d:f6:fa:9e:3f
}
Resolving Issues with Wired and Wireless Connections
When it comes to sending data to your router, you may be using a medium that is either wired or wireless (Wi-Fi) at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using - whether it’s 10.14.3, 11.1.8, or 12.0.6 - there are various tools available for troubleshooting. Unfortunately, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One extremely valuable tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings to the command-line interface and can be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless settings at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (even though there isn’t much interaction), you can run sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp with Finder using Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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