How Do You DiagnOSe Common Wifi Issues
Understanding Network Addressing
When using the Internet, you are assigned a unique Public IPv4 address such as 162.129.114.56 or an IPv6 address like 2000:82e6:4762:f7b1:f1b3:4626:2a5a:2f36. These addresses can be verified at https://test-ipv6.com/, and while they are essential for connectivity, conveying and managing them can be complex and error-prone, especially for those less familiar with technical details. Furthermore, historical data is not always readily available.
Navigating Websites
When accessing a website like https://lehner-dickens.info, the first step is to consult a DNS server to translate the URL’s host portion (lehner-dickens) and Top Level Domain (info) into an IP address, such as 132.35.170.102. In every web request, your computer and browser also transmit their type, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
The Significance of Default Gateways
The default gateway, usually automatically configured through DHCP, is a crucial component of network connections. Typical default gateway addresses, such as 10.87.156.213 (often ending in .1 or .254), serve as exit points for network traffic. For in-depth instructions on configuring default gateways for IPv6, refer to how-to-fix-ipv6-connectivity/, or use the following commands on Mac or Linux:
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 10.87.156.213 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 fe80:180:63fa:6f70:cc79%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): {179.2.63.111, 142.247.58.111}
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 71:04:15:a6:40:2f
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 69:66:5a:fe:b1:69
}
Solutions for Connectivity Issues with Wired or Wireless Networks
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Guidance for Mac Operating Systems
Regardless of whether you are using OSX/macOS versions like 10.15.3, 11.1.7, or 12.0.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Effective Built-in Tools for Troubleshooting
A 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. Additionally, the sysdiagnose tool can be used to generate a wide range of logs related to wireless connectivity, although much of the information is only point-in-time, similar to wdutil.
To run sysdiagnose in the background and write logs to /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 provide a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, as they are usually around 300MB.
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