How To Support OSX Issues
Understanding Internet Addressing Mechanisms
When using the Internet, you are assigned a Public IPv4 or IPv6 address, which can be checked from https://test-ipv6.com/. However, communicating these addresses or MAC addresses like 88:a1:c4:71:fa:e0 to non-technical individuals can be challenging and error-prone, without providing any historical context.
Navigating the World Wide Web
When accessing a website such as https://funk.name, your computer initially communicates with a DNS server to translate the URL’s host and Top Level Domain into an IP address, such as 115.12.239.4. Additionally, your computer and browser include detailed information in all web requests, such as the browser type.
Significance of Default Gateways
The default gateway, typically obtained via DHCP, is responsible for routing all of your computer’s traffic. For IPv6, detailed instructions can be found in our deep dive on how-to-fix-ipv6-connectivity/. On Mac or Linux, you can check your default gateway using the provided code.
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 10.77.216.53 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:af59:39a0:675f:66db%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): {43.134.119.143, 21.145.103.105}
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 88:a1:c4:71:fa:e0
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 c6:d2:00:a8:e8:c2
}
Resolve Issues with Wired or Wireless Connections
When transmitting data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layers.
Troubleshooting Methods for Apple macOS / OSX
Irrespective of the version of OSX/macOS you are operating on, whether it’s 10.13.4, 11.1.4, or 12.2.8, there are several tools available for resolving issues. However, these manual actions and scripts do not provide a consistent set of correlated values over time. This is where automated remote troubleshooting proves to be beneficial, especially for teams that are engaging in remote work and Work From Anywhere (WFA).
Utilize the Following Built-in Scripts for Assistance
An effective tool for OSX/macOS is the sudo wdutil info which provides a detailed dump of the current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool is a more comprehensive option for generating a wide range of logs related to wireless issues, though many of these are only relevant to a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in the /var/tmp/<blah>.tar.gz file. If you prefer to run it interactively (although there is minimal interaction), you can execute sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it will open Finder in the relevant location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which could be around 300MB or slightly more.
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