Fix MacOS Issues
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Understanding the Functionality of Internet Addressing
When using the Internet, you will be assigned a Public IPv4 address, such as 29.124.117.32, or an IPv6 address, such as 2000:4c31:39b1:ed:808b:82f0:3e98:91e. You can verify this using https://test-ipv6.com/. However, explaining or relaying these addresses, and even MAC addresses like 6a:4a:2c:ca:49:37, to those who are not tech-savvy can be prone to errors and become complex very quickly. Moreover, this does not provide any historical data (especially from past issues).
The Process of Accessing the Internet and Name Resolution
To access a website such as https://keeling-thiel.net, you initially contact a DNS server to convert the host portion (keeling-thiel) along with the Top Level Domain (net) of the URL into an IP address, like 9.99.159.122. Your computer and browser also send information about the type of web requests with every request, for instance: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
The Crucial Role of Default Gateways
Your default gateway is usually an automatically configured address through DHCP. You will receive a default gateway, such as 172.29.183.128 (although they generally end in .1 or .254 depending on the size of the scope), and this is where your computer sends all its traffic to be routed onwards. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/, but 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 172.29.183.128 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 fe80:3533:9bc1:b710:a668%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): {54.139.42.190, 109.93.177.120}
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 6a:4a:2c:ca:49:37
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 b9:3a:b1:24:93:71
}
Resolving Issues with Wired or Wireless Connectivity
When it comes to transferring data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are running OSX/macOS versions like 10.13.7, 11.5.8, or 12.0.9, there are various troubleshooting tools available. However, these manual actions and scripts fail to provide a set of interconnected values over a period of time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Commands and Scripts
A highly beneficial tool for OSX/macOS is sudo wdutil info, which allows you to access current wireless settings via the CLI and configure specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be employed to generate a wide range of logs, although much of it is only related to wireless settings just like wdutil.
To run it in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive (although minimal interaction) approach, you can run sudo /usr/bin/sysdiagnose and it will trigger a privacy warning. Running it in the background should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
Relevant Videos
P.S. Tips For Remote Network and Client Support
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