Troubleshoot Common Wifi Internet Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 129.75.125.90 or an IPv6 address like 2000:860a:b563:a469:6419:db34:eca4:2574. This can be verified at https://test-ipv6.com/. However, explaining these addresses or MAC addresses like a7:46:11:4c:64:58 to non-technical individuals can be challenging and error-prone. Unfortunately, this method does not provide historical data, especially when past issues arise.
Navigating the World Wide Web
When accessing a website such as https://langosh-lehner.net, you first connect to a DNS server to translate the host name (langosh-lehner) along with the Top Level Domain (net) of the URL into an IP address like 0.255.176.189. Interestingly, your computer and browser include their type in 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 Gateways
The default gateway is typically an automatically configured address through DHCP. This could be a default gateway like 10.224.110.153 (commonly ending in .1 or .254 based on the scope size), and all of your computer’s traffic is routed through this point. For IPv6, further details can be found at how-to-fix-ipv6-connectivity/, or you can check 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 10.224.110.153 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 fe80:1e19:96d2:959a:5ab1%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): {44.69.175.163, 250.140.192.204}
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 a7:46:11:4c:64:58
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 a8:1c:c7:65:5f:da
}
Fixing Connectivity Issues with Wired and Wireless Networks
When it comes to sending data to your router, you might be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.13.2, 11.1.4, or 12.3.6, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series 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).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Another comprehensive tool is the sysdiagnose tool, which can generate a variety of logs related to wireless issues.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will open Finder in the correct location for you to access the generated logs. Just keep in mind that the file sizes may be around 300MB.
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