How Can I Support MacOS Issues

Understanding Internet Addressing

When using the internet, you are assigned a Public IPv4 address, such as 87.184.36.57, or an IPv6 address, like 2000:2b13:6e77:4d36:df52:20f9:4fb1:3dec. These can be verified at https://test-ipv6.com/. However, relaying these addresses to individuals who are not technologically inclined, or even sharing MAC addresses such as 9a:d8:77:7a:68:06, can be prone to errors and quickly become complicated. Furthermore, this method does not provide historical data, particularly concerning past issues.

Navigating the Web

In order to reach a website, for example, https://breitenberg.name, you initially need to access a DNS server to convert the host component (breitenberg) along with the Top Level Domain (name) of the URL, to an IP address, such as 234.107.194.230. Notably, your computer and browser include its type in all web requests, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.

Understanding the Role of Default Gateways

The default gateway is typically an automatically configured address through DHCP. This default gateway, such as 10.216.84.238 (often ending in .1 or .254 based on the scope size), is where your computer directs all traffic to be routed. For IPv6, there is an in-depth analysis available at how-to-fix-ipv6-connectivity/, and verification can be done on Mac or Linux using:

/ code here

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  10.216.84.238    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:d4db:4f43:44a3:b62a%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): {211.227.173.113, 198.4.58.179}
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 9a:d8:77:7a:68:06
  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 4a:3b:8d:3e:4f:18
}

Resolve Issues with Wired or Wireless Connections

Your data may be transmitted through a wired or wireless (Wi-Fi) medium to reach your router at the physical and data layer.

Effective Solutions for Apple macOS / OSX Users

Regardless of whether you are using OSX/macOS versions such as 10.15.6, 11.1.6, or 12.3.3, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where remote troubleshooting automation is invaluable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).

Useful Built-in Scripts

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

To run sudo nohup /usr/bin/sysdiagnose -u & in the background, generating logs in /var/tmp/<blah>.tar.gz, or to run it interactively (with minimal interaction) by executing sudo /usr/bin/sysdiagnose and accepting the privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to the path /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which can be approximately 300MB or more.

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