How To Test Mac Issues
The Functionality of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 166.34.225.28, or an IPv6 address like 2000:1cdc:ae1f:d349:34e:a87b:f61c:61d5. You can verify your address by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, communicating these addresses, or MAC addresses like 1c:b3:0c:14:19:c0, can be prone to error and become complex. Moreover, this does not provide historical data, especially from previous issues.
Navigating the World Wide Web
When attempting to access a web page such as https://dickinson.co, you must first connect to a DNS server to translate the host portion (dickinson) combined with the Top Level Domain (co) of the URL into an IP address like 120.70.165.89. Interestingly, your computer and browser include its type with all web requests, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured via DHCP. It is assigned as a default gateway like 172.27.7.5 (usually ending in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onward. While we offer a more in-depth look at IPv6 connectivity in this blog: how-to-fix-ipv6-connectivity/, you can also verify 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 172.27.7.5 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 fe80:4aab:56f3:dd66:850e%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): {215.39.114.226, 239.238.177.225}
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 1c:b3:0c:14:19:c0
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 11:f2:3a:48:5a:ea
}
Resolving Issues with Wired and Wireless Connections
When it comes to sending data to your router, you may be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.14.2, 11.2.8, or 12.2.9, there are various troubleshooting tools available. However, these tools do not provide a series of correlated values over time, making it difficult to pinpoint the root cause of the issue. This is where automated remote troubleshooting becomes particularly beneficial, especially for teams that have adopted remote work and Work From Anywhere (WFA) policies.
Utilizing In-Built Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of the information is only relevant to a specific point in time in relation to wireless settings, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively by using sudo /usr/bin/sysdiagnose and handling the privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G, but be cautious of the large file sizes of around 300MB.
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