Troubleshoot OSX Issues
Understanding Internet Addressing
When using the Internet, you will be assigned a Public IPv4 or IPv6 address, such as 50.49.125.241 or 2000:b7d9:dbd:5d75:4628:5fd8:5950:60ee. You can verify your address at https://test-ipv6.com/. However, for those who are not tech-savvy, communicating these addresses or even MAC addresses like 25:6a:26:81:d1:6f can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, especially for past issues.
Navigating the Web
Accessing a webpage like https://cruickshank-funk.name begins with contacting a DNS server to translate the host portion (cruickshank-funk) and the Top Level Domain (name) of the URL into an IP address, such as 101.135.40.18. Your computer and browser include its type with all web requests, for example:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
The Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP. It usually ends in .1 or .254, depending on the scope size, such as 10.146.55.76, and is where your computer sends all its traffic to be routed onwards. For IPv6, you can refer to the detailed 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 10.146.55.76 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:c7e1:b47e:4d8c:20ad%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): {6.146.199.132, 61.244.91.133}
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 25:6a:26:81:d1:6f
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 4b:a5:a2:73:10:5f
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, the choice between a wired or wireless (Wi-Fi) medium at the physical and data layer can lead to various troubleshooting challenges.
Helpful Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS versions such as 10.15.1, 11.6.6, or 12.0.1, there are several troubleshooting tools available. Unfortunately, these manual actions and scripts do not provide a detailed set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that have embraced remote work and Work From Anywhere (WFA) setups.
Effective Built-in Utilities
An incredibly useful tool on OSX/macOS is the sudo wdutil info command, which provides a comprehensive display of current wireless settings in the Command Line Interface (CLI), and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool offers a more comprehensive approach by generating a wide range of logs, although much of it is only relevant to wireless connections, similar to wdutil.
To run it in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively with the command sudo /usr/bin/sysdiagnose, which will provide a privacy warning. When not run in the background, it should open Finder in the correct location, and if not, you can navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. Just keep in mind that the file sizes are approximately 300MB.
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P.S. Tips For Remote Network and Client Support
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