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. –
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.

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

Video Title Channel
Securing macOS Big Sur Hands-On Mac
Spotlight on Spotlight - Hands-On Mac 7 Hands-On Mac
macOS Big Sur - What's New in Apple macOS 11 Hands-On Mac
On the Road to Big Sur 2 - Compatibility Hands-On Mac
Mac Activity Monitor - How to Troubleshoot Your Mac Hands-On Mac
Table 1.0 - Video Help



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