How Can I DiagnOSe Apple No-access
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 159.22.9.210 or an IPv6 address like 2000:10c7:9944:35d7:f210:b99:d9c9:28ed. You can verify these addresses from https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses accurately, or even referencing MAC addresses like 9d:08:84:f1:a1:18, can be prone to errors and become complex rather quickly. Moreover, this method omits any historical data, especially relating to past issues.
Navigating the World Wide Web
In order to access a website, such as https://farrell-connelly.com, your system first contacts a DNS server to translate the URL’s host portion (farrell-connelly) in combination with the Top Level Domain (com) to an IP address like 188.85.38.142. Additionally, whenever you make web requests, your computer and browser transmits its type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
By default, your gateway is usually an address that is automatically configured via DHCP. Typically, you receive a default gateway such as 10.191.132.250 (although they typically end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed further. For IPv6, we have a comprehensive examination on how-to-fix-ipv6-connectivity/, or you can perform a diagnostic check on Mac or Linux using the following command:
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 10.191.132.250 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 fe80:6103:edee:7930:3881%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): {94.85.19.179, 170.63.150.49}
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 9d:08:84:f1:a1:18
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 65:9c:c9:4a:70:62
}
Resolving Connectivity Issues: Wired vs Wireless
When it comes to transmitting data to your router, you might be using a wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple’s macOS / OSX Devices
Regardless of whether you are using OSX or macOS version 10.15.1, 11.6.4, or 12.0.8, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes beneficial, especially for teams adapting to remote work and Work From Anywhere (WFA) setups.
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Alternatively, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless settings, much like wdutil.
Running the command sudo nohup /usr/bin/sysdiagnose -u & in the background will create logs in /var/tmp/<blah>.tar.gz for you. For an interactive (though minimal interaction) experience, you can run sudo /usr/bin/sysdiagnose and be prompted with 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. Be mindful of the file sizes, which are generally around 300MB.
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