Test OSX Issues
Understanding Internet Addressing Mechanics
When connecting to the Internet, you are assigned a Public IPv4 address, such as 249.187.221.210, or an IPv6 address, like 2000:f694:391c:6067:3a42:5aa8:8861:1879. You can verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to individuals who are not technologically savvy, or even discussing MAC addresses, such as 16:81:34:5e:5b:67, can be prone to errors and become complex. Furthermore, this method does not provide historical data, especially regarding past issues.
Navigating the World Wide Web
In order to access a website like https://williamson.net, you first contact a DNS server to convert the host portion (williamson) combined with the Top Level Domain (net) of the URL to an IP address, such as 24.40.67.252. Your computer and browser include its type in all web requests, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
Exploring the Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP. A default gateway, such as 192.0.0.25 (although they usually end in .1 or .254 depending on the scope size), is where your computer forwards all its traffic for further routing. To learn more about IPv6, visit our in-depth guide on how-to-fix-ipv6-connectivity/, or 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 192.0.0.25 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 fe80:9204:6c14:4cdc:3de3%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): {35.132.91.222, 1.12.239.55}
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 16:81:34:5e:5b:67
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 c5:a9:d4:38:28:f7
}
Troubleshooting Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, the physical and data layers may involve either a wired or wireless (Wi-Fi) medium.
Resolving Connectivity Problems on Apple macOS / OSX
Regardless of whether you are using OSX/macOS versions such as 10.12.5, 11.2.7, or 12.3.8, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of interconnected values over time. This is where automated remote troubleshooting becomes essential, especially for teams that are adopting remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
An extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the command line interface and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although most of them pertain to wireless settings and are only relevant at a specific point in time, 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 &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will issue a privacy warning. When not run in the background, it should open Finder in the correct location, allowing you to navigate to the path /var/tmp or use Finder with Cmd+Shift+G to navigate. Keep in mind that the file sizes are approximately 300MB.
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