Troubleshoot Apple No-access

Understanding Internet Addressing Mechanisms

When using the Internet, individuals may be assigned a Public IPv4 address, such as 238.216.240.29, or an IPv6 address, like 2000:a6b:cda2:ccb8:abec:e6e6:9456:5c6a. The verification of these addresses can be done via https://test-ipv6.com/. However, the communication and referencing of these addresses, as well as MAC addresses like 59:98:5b:91:d6:3c, can be prone to errors and complexity, especially for those who are not technologically inclined. Moreover, this method does not provide any historical data, especially regarding previous issues that may have arisen.

Navigating the World Wide Web

When attempting to access a web page, such as https://schiller-kshlerin.name, the initial step involves contacting a DNS server to transform the host segment (schiller-kshlerin) combined with the Top Level Domain (name) of the URL into an IP address, for example, 171.33.83.176. With each web request, your computer and browser transmit their type, such as
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

Typically, your default gateway is an address that is automatically configured via DHCP. This may appear as a default gateway like 192.168.86.110 (often ending in .1 or .254 based on the scope size), and serves as the destination where your computer forwards all of its traffic for further routing. For IPv6, an in-depth guide on how-to-fix-ipv6-connectivity/ is available, while on Mac or Linux, verification can be done 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  192.168.86.110    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:eb54:ec8f:dec4:6ba5%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): {107.79.34.97, 110.224.8.87}
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 59:98:5b:91:d6:3c
  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 4a:d6:cc:80:46:0c
}

Resolve Wired or Wireless Connectivity Issues

When transferring data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.

Troubleshooting Tips for Apple macOS / OSX

Regardless of whether you are using OSX/macOS version 10.11.5, 11.6.8, or 12.0.6, there are various troubleshooting tools available. However, these manual methods 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 Work From Anywhere (WFA).

Useful Built-in Scripts

One of the useful tools on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings and can be configured to generate specific troubleshooting logs. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although most of it is only relevant to wireless settings, similar to wdutil.

sudo nohup /usr/bin/sysdiagnose -u & can be used to run it in the background and it will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (though there is minimal interaction), you can utilize
sudo /usr/bin/sysdiagnose, which will trigger 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. However, be mindful of the file sizes, which can be around 300MB.

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Table 1.0 - Video Help