How Do You Troubleshoot Common Wifi Connectivity
Explaining Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 160.151.229.214 or an IPv6 address like 2000:dfcf:519a:17e8:6b77:eb97:29c9:372c. You can verify this information at https://test-ipv6.com/. However, conveying these addresses and MAC addresses like 07:77:47:8b:37:64 to those who are not tech-savvy can be prone to errors and become complex. Furthermore, it does not provide historical data, especially when resolving past issues.
Navigating the World Wide Web
When accessing a website like https://friesen.biz, the initial step involves contacting a DNS server to convert the host portion (friesen) and the Top Level Domain (biz) of the URL into an IP address such as 91.54.162.253. Your computer and browser include its type in all web requests, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway is typically an address configured automatically through DHCP. You are assigned a default gateway like 192.168.19.110 (usually ending in .1 or .254 based on the scope size), and this is where your computer sends all its traffic to be routed further. For IPv6, there is a detailed guide available at how-to-fix-ipv6-connectivity/ and 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 192.168.19.110 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:c3d2:b4f4:e678:fc98%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): {174.204.70.65, 71.213.111.102}
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 07:77:47:8b:37:64
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 9d:80:b1:0c:2f:16
}
Solutions for Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you may encounter connectivity problems at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting Techniques for Apple macOS / OSX
Regardless of which version of OSX/macOS you are operating on, whether it’s 10.11.1, 11.1.4, or 12.0.8, there are various troubleshooting tools available. However, these tools do not provide a series of correlated values over time, which is crucial for effective troubleshooting. This is where automated remote troubleshooting becomes essential, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Commands for Troubleshooting
One of the useful tools on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are only relevant at a specific point in time in relation to wireless connectivity, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, 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 and it will provide a privacy warning. Running it without the background process should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Be mindful of the file sizes, which are typically around 300MB.
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