Fix Apple Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 81.174.99.15 or an IPv6 address like 2000:2aad:975a:e2d8:dd1c:e3e0:e600:2c84. This can be verified on https://test-ipv6.com/. However, conveying these addresses, or even MAC addresses like bb:59:dd:17:7c:61, can be error-prone and complex, especially for non-technical individuals. Moreover, this method does not offer historical data, making it difficult to troubleshoot prior issues.
Navigating the World Wide Web
When visiting a webpage such as https://rodriguez.name, you first connect to a DNS server to translate the host part (rodriguez) and the Top Level Domain (name) of the URL into an IP address like 206.88.109.252. Each web request sent by your computer and browser includes its type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Your default gateway is typically an automatically generated address through DHCP. It usually ends in .1 or .254, depending on the scope size, such as 172.20.251.99. This is where your computer forwards all of its traffic to be routed onwards. For IPv6, you can find more information by visiting how-to-fix-ipv6-connectivity/ or by using the following commands on Mac or Linux:
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 172.20.251.99 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 fe80:69e1:430d:fcf7:659e%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): {185.129.141.171, 48.204.73.51}
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 bb:59:dd:17:7c:61
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 1f:17:26:1e:ef:2f
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layers to send information to your router.
Strategies for Apple macOS / OSX Troubleshooting
No matter which version of OSX/macOS you are using, whether it’s 10.15.1, 11.4.3, or 12.3.9, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and the concept of Work From Anywhere (WFA).
Effective Built-in Utilities for Troubleshooting
One particularly useful tool on OSX/macOS is sudo wdutil info which provides a detailed snapshot of current wireless settings to the command line interface, and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool offers a more comprehensive option for generating diverse logs, although many are only relevant to wireless settings, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz, or to run it interactively and receive a privacy warning, you can enter sudo /usr/bin/sysdiagnose which should open Finder in the correct location or allow navigation to /var/tmp, or utilize Finder with Cmd+Shift+G to direct Finder to the path. However, be cautious of the file sizes, which are approximately 300MB.
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