Troubleshoot Apple Internet
The Functioning of Internet Addressing
When using the Internet, you will be assigned a Public IPv4 address, such as 107.62.166.144, or an IPv6 address, such as 2000:1b14:c1aa:3e48:87f2:5b0b:25f3:e19. A quick way to verify this is through https://test-ipv6.com/. However, relaying these addresses to individuals who are not tech-savvy, or even mentioning MAC addresses like 23:4d:37:bd:62:48, can be prone to errors and can become complex rather rapidly. Furthermore, these methods do not offer any past data, especially when addressing past issues.
Connecting to Online Content
Accessing a webpage like https://lockman-stracke.name involves initially connecting to a DNS server to convert the host portion (lockman-stracke) in combination with the Top Level Domain (name) of the URL to an IP address like 230.143.110.133. Every request your computer and browser makes includes its type, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured through DHCP. An example of a default gateway would be 192.168.198.149 (the last digits are usually .1 or .254 based on the scope size) and this is where your computer sends all of its traffic to be routed further. To explore more about IPv6, you can refer to 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 192.168.198.149 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 fe80:140d:7cdf:1980:1821%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): {91.167.249.216, 48.164.214.2}
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:ce:37:bd:60:46
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 84:e7:9c:a2:fd:91
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX or macOS versions like 10.12.7, 11.6.2, or 12.1.9, there are numerous troubleshooting tools available. However, these tools do not provide a series of correlated values over time, making automated remote troubleshooting essential, especially for teams that work remotely or embrace the Work From Anywhere (WFA) concept.
Leveraging Built-in Scripts for Assistance
On OSX/macOS, the sudo wdutil info tool is extremely useful as it provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Moreover, the sysdiagnose tool can 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 write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use sudo /usr/bin/sysdiagnose and follow the privacy warning. The generated logs can be found in the /var/tmp directory or accessed using Finder with Cmd+Shift+G to navigate to the correct location. Note that the file sizes are approximately 300MB.
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