Understand Apple Issues
Understanding Internet Address Allocation
When connecting to the Internet, you are assigned a unique public IP address, which can be in the form of a Public IPv4 address such as 57.72.224.176 or an IPv6 address like 2000:16cb:9486:a0e:cda2:300c:3db2:36b7. These addresses can be verified using tools like https://test-ipv6.com/. However, conveying and managing these addresses, particularly for non-technical users, or dealing with MAC addresses like e2:2a:c5:c0:5c:c7 can be prone to errors and become complex. Moreover, it lacks historical data, which is crucial for diagnosing past issues.
Navigating the World Wide Web
Accessing a website, such as https://morissette.info, involves first contacting a DNS server to convert the combination of the host (morissette) and the Top Level Domain (info) into an IP address, like 197.86.36.57. Your computer and browser, by default, disclose their specifications with each web request, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
The default gateway is typically assigned automatically through DHCP and often appears as an address like 10.78.127.129 (commonly ending in .1 or .254, depending on the scope size). This is the central point through which your computer forwards all of its traffic. For troubleshooting IPv6 connectivity, detailed guidance is available at how-to-fix-ipv6-connectivity/, and on Mac or Linux systems, the status can be verified 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 10.78.127.129 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:dd47:e3af:e98f:c53f%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): {137.173.251.63, 247.108.162.85}
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 e2:2a:c5:c0:5c:c7
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 0d:82:0e:6e:45:5d
}
Resolving Issues with Wired and Wireless Connections
When it comes to transferring data to your router, you may be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Users
No matter if you have OSX or macOS version 10.14.3, 11.2.4, or 12.2.5, there are various troubleshooting tools available. However, these tools and manual actions do not provide a set of interconnected values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that are adopting remote work and Work From Anywhere (WFA) approach.
Useful Built-in Scripts
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a detailed dump of current wireless settings through the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is related to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and create logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. To run it interactively, use the command sudo /usr/bin/sysdiagnose, which will give a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Just be cautious of the file sizes, which are approximately 300MB.
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