How To Check Mac Issues
The Functionality of Internet Addressing
When using the Internet, individuals are assigned with either a Public IPv4 address such as 219.165.147.186 or an IPv6 address like 2000:fdfe:60f3:2383:2750:992e:2ed:1929. One can verify this information by visiting https://test-ipv6.com/. However, attempting to communicate these addresses or MAC addresses such as c0:31:80:ad:80:7f can be prone to errors and become complex, especially for those who are not tech-savvy. Furthermore, this approach does not provide any historical data, particularly when attempting to address previous issues.
Navigating the World Wide Web
In the process of accessing a web page like https://swift-jaskolski.co, the first step involves consulting a DNS server to convert the hostportion (swift-jaskolski) combined with the Top Level Domain (co) of the URL into an IP address, such as 36.174.197.78. When making web requests, your computer and browser transmit its type along with the request, 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 configured address via DHCP, a default gateway, such as 10.142.17.245 (commonly ending in .1 or .254 based on the scope size), is where your computer directs all its traffic to be routed onward. To delve deeper into IPv6 connectivity, refer to the guide on how-to-fix-ipv6-connectivity/, or 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 10.142.17.245 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:ec9a:c5b9:2a5d:92c1%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): {142.248.81.21, 40.185.229.236}
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 c0:31:80:ad:80:7f
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 f8:ae:2d:de:c2:2a
}
Troubleshoot and Resolve Connectivity Issues on Wired or Wireless Networks
When it comes to sending data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
No matter which version of OSX/macOS you are currently using, whether it’s 10.13.9, 11.3.9, or 12.2.6, there are various resources available for troubleshooting connectivity issues. However, these methods and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that practice remote work and Work From Anywhere (WFA).
Utilizing In-Built Scripts for Support
One of the most useful tools 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. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of the information is only relevant to wireless connectivity, similar to the wdutil command.
To run the sysdiagnose tool 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 sudo /usr/bin/sysdiagnose but bear in mind that the file sizes can be around 300MB. After running the command, Finder should open in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G.
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