Fix Apple No-access
Understanding Internet Addressing
When using the Internet, you are assigned an address such as 159.154.248.54 for IPv4 or 2000:eb40:84a1:315c:5495:9ffa:d6a4:281f for IPv6. A useful tool for checking your address is https://test-ipv6.com/. However, for those not familiar with technical aspects, conveying and communicating these addresses, or even MAC addresses like 7c:aa:ea:02:9c:48, can be error-prone and complex. Furthermore, this method lacks historical data, especially when dealing with past issues.
How Websites Are Accessed
When trying to reach a website like https://sanford-jakubowski.com, the first step is to contact a DNS server to translate the combination of the host name (sanford-jakubowski) and the Top Level Domain (com) into an IP address, such as 111.248.106.66. Additionally, your computer and browser send specific information with every web request, such as Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
The Significance of Default Gateways
Default gateways are typically automatically assigned addresses through DHCP, with examples like 192.168.105.177 (commonly ending in .1 or .254 based on the scope size). This is where all of your computer’s traffic is sent for further routing. For a detailed guide on IPv6, refer to how-to-fix-ipv6-connectivity/ or check 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 192.168.105.177 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 fe80:27f8:2e50:3552:5f3f%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): {134.136.246.210, 80.143.44.71}
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 7c:aa:ea:02:9c:48
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 26:62:48:12:12:15
}
Troubleshooting Connectivity Issues
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS version 10.15.9, 11.1.2, or 12.0.2, there are various tools available for troubleshooting connectivity issues. However, these manual methods and scripts fail to provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have adopted remote work and Work From Anywhere (WFA) policies.
Useful Built-in Scripts
A valuable tool for OSX/macOS users is the sudo wdutil info, which provides a dump of current wireless settings to the CLI, and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although many are only relevant to wireless issues, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use 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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