How Can I Understand Apple No-access
Functioning of Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address such as 89.190.67.203 or an IPv6 address like 2000:139f:5652:2f0b:3e53:7210:20b7:1197. These addresses can be verified at https://test-ipv6.com/. However, for those who are not technologically inclined, communicating these addresses or MAC addresses like ae:c7:71:ac:27:c2 can be prone to errors and can quickly become complex. Moreover, this approach does not provide historical data, especially regarding past issues.
Navigating the Internet
When attempting to access a website such as https://nolan.net, the initial step is to contact a DNS server to convert the host portion (nolan) in combination with the Top Level Domain (net) of the URL into an IP address, such as 225.240.42.177. Your computer and browser identify themselves with specific details in all web requests, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
Usually, your default gateway is an address that is automatically configured through DHCP. This gateway, such as 10.85.93.65, (typically ending in .1 or .254 depending on the scope size), is the point to which your computer directs all its traffic to be routed further. For IPv6, a more detailed examination can be found at how-to-fix-ipv6-connectivity/, but you can verify on Mac or Linux using:
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 10.85.93.65 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:f6dc:dda5:db46:8c59%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): {231.144.210.213, 149.38.11.109}
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 ae:c7:71:ac:27:c2
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 9d:e5:5e:31:45:46
}
Tips for Resolving Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you may be using a wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Steps for Apple macOS / OSX Users
Regardless of which version of OSX/macOS you have - whether it’s 10.11.8, 11.4.8, or 12.1.3 - there are various troubleshooting tools at your disposal. However, manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Utilizing In-Built Scripts for Assistance
One incredibly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless related settings to the CLI and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant at a specific point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose which will prompt 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. Keep in mind that the file sizes are approximately 300MB.
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