Troubleshoot Common Wifi Issues
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a public IP address, such as 65.152.173.210 for IPv4 or 2000:23a3:bf82:108f:a3cb:4a28:d95b:3fe0 for IPv6. You can verify this information by visiting https://test-ipv6.com/. However, expressing these addresses, or even MAC addresses like 02:62:3d:5c:65:b5, can be challenging for those who are not tech-savvy. In addition, this does not provide any historical data, especially when dealing with past issues.
Navigating the World Wide Web
Accessing a website, such as https://pacocha-paucek.net, involves querying a DNS server to translate the URL’s host portion (pacocha-paucek) and Top Level Domain (net) into an IP address, like 62.236.142.31. When making web requests, your computer and browser include information about their type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
The default gateway is typically assigned automatically via DHCP and is represented by an address like 172.23.141.71 (often ending in .1 or .254 depending on the scope size). This is where your computer directs all its traffic to be routed elsewhere. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity, and you can check on Mac or Linux by using the following command:
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 172.23.141.71 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:b26c:5ec3:b3b6:5403%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): {101.8.170.130, 223.206.0.144}
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 02:62:3d:5c:65:b5
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 48:fd:28:41:35:1a
}
Resolve Issues with Wired or Wireless Connections
When sending data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Steps for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are using - whether it’s 10.13.2, 11.2.2, or 12.2.3 - there are various tools available for resolving connectivity issues. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly useful, especially for teams that have embraced remote work and the concept of Work From Anywhere (WFA).
Useful Built-in Scripts
A valuable tool for OSX/macOS users is the sudo wdutil info command, which provides a dump of the current wireless settings to the command line interface and can be configured to generate specific logs for troubleshooting purposes. Moreover, the sysdiagnose tool can be utilized to generate a comprehensive set of logs, although most of it relates to wireless issues just like 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 &. Alternatively, if you prefer to run it interactively, you can use the command 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 using Finder with Cmd+Shift+G. Keep in mind that the file sizes will be approximately 300MB.
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