DiagnOSe Wifi Issues
Explanation of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 44.101.16.215, or an IPv6 address, such as 2000:6458:3f7:5889:5a8d:f0fa:f9ce:f0b3. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not technologically inclined, expressing these addresses or even identifying MAC addresses like 66:8d:de:ae:08:fb can easily lead to errors and confusion. Furthermore, this method does not provide any historical data, particularly when encountering previous issues.
The Process of Accessing the Web Page
In order to access a web page such as https://huel.org, you first contact a DNS server to convert the host portion (huel) combined with the Top Level Domain (org) of the URL into an IP address, for example, 174.190.72.58. Additionally, your computer and browser transmit their type in all web requests, such as 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
The default gateway is typically assigned automatically through DHCP and manifests as an address like 10.26.166.158 (although they usually end in .1 or .254 based on the scope). This is the location where your computer sends all of its traffic to be directed to the appropriate destination. For IPv6, we delve deeply into the topic in our article how-to-fix-ipv6-connectivity/, or you can verify it 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 10.26.166.158 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:a149:56a5:f24a:b5c5%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): {36.66.220.137, 144.230.57.124}
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 66:8d:de:ae:08:fb
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 28:dc:09:00:b2:1c
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be utilizing either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
No matter which version of OSX/macOS you are currently using - whether it’s 10.15.8, 11.5.3, or 12.0.2 - there are various tools available for troubleshooting connectivity issues. However, these manual actions and scripts do not provide a continuous set of related values over time. This is where automated remote troubleshooting becomes particularly beneficial, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Effective Built-in Scripts
A useful tool for OSX/macOS users is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless settings at a specific point in time, much like wdutil.
To run sysdiagnose in the background and write logs to /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, 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 are approximately 300MB.
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