How Do You Troubleshoot MacOS Issues

Understanding Internet Addressing

When connecting to the Internet, you are assigned a Public IPv4 address, such as 46.214.78.155, or an IPv6 address, like 2000:f27:93a:faf1:bd8a:9511:f0a:cec4. You can verify this information by visiting https://test-ipv6.com/. However, attempting to communicate these addresses or MAC addresses, like 8d:75:e6:8b:4a:7f, can be error-prone and complicated for non-technical individuals. Moreover, this information lacks historical data from previous issues.

Accessing Websites

To access a web page, such as https://smith.com, your computer first contacts a DNS server to translate the host portion (smith) and the Top Level Domain (com) of the URL into an IP address, like 232.132.64.203. Along with every web request, your computer and browser send its type, for example:

Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)

The Significance of Default Gateways

Typically, your default gateway is an automatically configured address assigned via DHCP, such as 172.16.158.196 (usually ending in .1 or .254 depending on the scope size). This is where your computer sends all its traffic to be routed onwards. For IPv6 issues, there is an in-depth guide available at how-to-fix-ipv6-connectivity/. In Mac or Linux, you can check this with:

<br>

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  172.16.158.196    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:cabd:b808:f20a:767e%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): {74.77.17.71, 41.109.147.178}
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 8d:75:e6:8b:4a:7f
  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 19:53:d7:a2:e7:18
}

Solutions for Resolving Issues with Wired or Wireless Connections

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

Troubleshooting Options for Apple macOS / OSX Users

Regardless of whether you are using OSX/macOS versions such as 10.15.7, 11.3.1, or 12.1.6, there is a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).

Useful Built-in Tools

On OSX/macOS, a very useful tool is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Another comprehensive tool is sysdiagnose, which can generate a wide range of logs related to wireless (though most are only point-in-time logs, similar to wdutil).

To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can 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, but be cautious of the large file sizes (about 300MB or more).

Possibly Helpful Videos

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Table 1.0 - Video Help