How Do You Fix OSX No-access
The Functioning of Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 or IPv6 address. You can verify your address at https://test-ipv6.com/. However, explaining these addresses to non-technical individuals, or identifying MAC addresses like 98:a6:e7:5c:ce:0d, can be error-prone and complex. Moreover, this does not provide historical data, particularly from previous issues.
Navigating the World Wide Web
Accessing a website such as https://lebsack-renner.info involves initially consulting a DNS server to convert the combination of the host portion (lebsack-renner) and the Top Level Domain (info) of the URL into an IP address like 167.109.248.97. Furthermore, your computer and browser include its type in all web requests, e.g., Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.
The Significance of Default Gateways
The default gateway is typically an address assigned through DHCP. It commonly ends in .1 or .254 based on the scope size, such as 10.203.83.206, and serves as the location to which your computer sends all its traffic for routing. For IPv6, detailed instructions are provided in how-to-fix-ipv6-connectivity/, but you can verify 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 10.203.83.206 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:ba0c:9084:d86:368c%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): {158.134.171.174, 64.93.2.23}
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 98:a6:e7:5c:ce:0d
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:11:0c:ca:49:be
}
Resolving Issues with Wired and Wireless Connectivity
When it comes to transmitting data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Techniques for Apple macOS / OSX
Regardless of whether your operating system is OSX/macOS version 10.11.1, 11.2.4, or 12.1.7, there are various methods for troubleshooting. However, the manual actions and scripts available do not provide a set of interconnected values over a period of time. This is where automated remote troubleshooting becomes particularly valuable, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Utilizing Pre-installed Scripts for Assistance
A useful tool available on OSX/macOS is sudo wdutil info, which allows for the CLI to display current wireless settings and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is relevant to wireless settings only, similar to wdutil.
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive (albeit with minimal interaction) experience, use sudo /usr/bin/sysdiagnose and be warned about privacy. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to direct it to the path. Keep in mind that the file sizes are approximately 300MB.
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