How Can I Check Mac Issues
The Functioning of Internet Addressing
When using the internet, individuals may encounter a Public IPv4 address such as 33.124.41.149 or an IPv6 address like 2000:b9f7:278c:2adf:981f:b62a:f261:1a3a. This information can be verified at https://test-ipv6.com/. However, conveying these addresses to those who are not technically inclined, or even mentioning MAC addresses like dd:ed:69:ec:7d:76, can be prone to errors and can become complex very quickly. Furthermore, this method does not provide any historical data, especially when previous issues have arisen.
Reaching Websites
To access a web page like https://schaden.net, the first step is to contact a DNS server to convert the host section (schaden) in combination with the Top Level Domain (net) of the URL to an IP address such as 28.181.200.221. During all web requests, your computer and browser send their type, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured through DHCP. It usually takes the form of a default gateway like 192.0.0.45 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onward. For IPv6, more in-depth information is available at how-to-fix-ipv6-connectivity/, or you can perform a 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 192.0.0.45 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 fe80:4b20:de1e:df66:e3e5%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): {252.249.36.246, 230.36.54.107}
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 dd:ed:69:ec:7d:76
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 96:71:a5:f0:ab:61
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Finding Solutions for Apple macOS / OSX Systems
Regardless of the version of OSX/macOS you are currently using, such as 10.13.2, 11.6.8, or 12.1.6, there are various troubleshooting tools available. However, these tools, both manual and scripted, do not provide a continuous set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) approach.
Leveraging Built-in Scripts for Assistance
A highly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool offers a more comprehensive solution by generating a wide range of logs (although, much of it is only pertinent to wireless settings, 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 aware of the large file sizes of around 300MB. After running the command in the background, it should open Finder in the appropriate location, allowing you to navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the files. However, be cautious of the large file sizes, typically around 300MB.
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