How To DiagnOSe Wifi Issues
Understanding Internet Addressing
The addressing system used on the Internet assigns unique IP addresses to devices, such as a Public IPv4 address like 202.27.147.129 or an IPv6 address like 2000:3f48:9da8:815d:132e:cb82:60de:bc7b. You can verify your IP address using websites like https://test-ipv6.com/. However, for those who are not technically inclined, trying to communicate these addresses or MAC addresses like 30:83:dd:9f:47:27 can be prone to errors and become complex rather quickly. Moreover, this method does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When attempting to access a website such as https://zieme.net, the process begins with a request to a DNS server. This server translates the host portion (zieme) combined with the Top Level Domain (net) of the URL into an IP address, such as 192.253.241.131. Remarkably, your computer and browser reveal specific details with all web requests, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Significance of Default Gateways
Commonly, the default gateway is an address that is automatically configured via Dynamic Host Configuration Protocol (DHCP). This default gateway typically appears as an address like 192.168.157.91 (often ending in .1 or .254, depending on the scope size), and it serves as the point to which your computer sends all its traffic to be routed onwards. If you want to troubleshoot IPv6 connectivity, you can find a comprehensive guide at how-to-fix-ipv6-connectivity/. Alternatively, you can check on Mac or Linux using the following commands:
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 192.168.157.91 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 fe80:415c:1247:204:a5da%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): {36.82.22.100, 54.109.148.165}
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 30:83:dd:9f:47:27
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 f5:54:51:4c:e3:3f
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Troubleshooting
Regardless of whether you are using OSX/macOS version 10.15.6, 11.2.6, or 12.3.2, there are various troubleshooting tools available. However, these tools do not provide a series of correlated values over time, making it challenging to identify the root cause of the issue. This is where automated remote troubleshooting becomes essential, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Utilities
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a detailed dump of current wireless settings to the CLI. It can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a comprehensive set of logs, although many of them are only relevant to a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs, you can use the command sudo nohup /usr/bin/sysdiagnose -u &, which will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose and it will open Finder in the correct location. Alternatively, you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the files. Keep in mind that the file sizes are approximately 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
