How To Understand Common Wifi Internet Issues
Understanding the Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 56.154.68.142, or an IPv6 address, like 2000:a971:83d9:412d:56fb:f07b:56c7:38bf. It is possible to verify this at https://test-ipv6.com/. However, attempting to convey these addresses to individuals who are not well-versed in technology, or even mentioning MAC addresses like 0a:d1:88:98:fb:9c, can be prone to errors and can become complex rather quickly. Moreover, this method does not provide any historical data, particularly from previous issues.
Navigating the World Wide Web
Upon entering a web page, such as https://lind.net, the first step is to access a DNS server to convert the host component (lind) along with the Top Level Domain (net) of the URL to an IP address, such as 165.28.150.159. Additionally, your computer and browser reveal their specifications with each web request, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of the Default Gateways
Typically, your default gateway is an automatically configured address obtained from DHCP. An example of a default gateway is 10.8.125.116 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer directs all its traffic to be routed onwards. For IPv6, you can delve deeper into this topic on how-to-fix-ipv6-connectivity/ or you can verify this on Mac or Linux with:
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 10.8.125.116 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 fe80:6bc5:c040:f4eb:3535%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): {111.229.239.36, 0.242.110.148}
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 0a:d1:88:98:fb:9c
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 79:0e:9c:63:a4:24
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are using, such as 10.12.3, 11.6.1, or 12.3.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that adopt remote work and Work From Anywhere (WFA).
Useful Built-in Scripts for Troubleshooting
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related 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, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which 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 manually. Keep in mind that the file sizes are approximately 300MB.
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