How Do You Support MacOS Internet Connection

How Addressing on the World Wide Web Works

When you browse the internet, you will receive a public IPv4 address such as 203.120.52.127 or an IPv6 address like 2000:1942:3763:31d1:8c68:d364:7eeb:46be. You can verify this at https://test-ipv6.com/. However, for individuals who aren’t familiar with technology, attempting to communicate these addresses or even mentioning MAC addresses like 5e:04:bd:45:c6:fb can be prone to errors and quickly become complex. Additionally, this method does not provide any historical data.

Navigating Websites

In order to access a website like https://schaefer.org, you initially contact a DNS server to convert the combination of the host portion (schaefer) and the Top Level Domain (org) of the URL into an IP address like 86.235.227.72. Your computer and browser actually sends its type with all web requests, as shown by the following example:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A

The Significance of Default Gateways

Your default gateway is typically an automatically assigned address via DHCP. You will receive a default gateway like 192.168.176.209 (although they generally end in .1 or .254 depending on the scope size) and this is where your computer forwards all its traffic to be routed further. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/, but you can also check on Mac or Linux with:

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  192.168.176.209    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   fe80:5148:6ff0:5fd3:7314%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): {249.37.237.92, 35.31.104.33}
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 5e:04:bd:45:c6: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 71:be:f0:f4:e0:f5
}

Resolving Issues with Wired and Wireless Connections

When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.

Troubleshooting Techniques on Apple macOS / OSX

No matter which version of OSX/macOS you are using, whether it’s 10.13.5, 11.4.3, or 12.0.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).

Useful Built-in Commands

One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a comprehensive range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.

Running sudo nohup /usr/bin/sysdiagnose -u & in the background will create logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (even though there isn’t much interaction), you can use
sudo /usr/bin/sysdiagnose, which will give a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. However, be mindful of the file sizes, which are approximately 300MB.

Possibly Helpful Videos

Video	Title	Channel
	On the Road to Big Sur 2 - Compatibility	Hands-On Mac
	Mac Activity Monitor - How to Troubleshoot Your Mac	Hands-On Mac
	Securing macOS Big Sur	Hands-On Mac
	macOS Big Sur - What's New in Apple macOS 11	Hands-On Mac
	Secret Mac Boot Commands - Mac Boot Key Combinations	Hands-On Mac

Table 1.0 - Video Help