How Can I Understand Mac No-access
The Fundamentals of Internet Addressing
When using the Internet, individuals may be assigned Public IPv4 addresses, such as 179.89.70.39, or IPv6 addresses, like 2000:658d:bb51:a4f3:1c38:6e48:c807:b974. This information can be verified by visiting https://test-ipv6.com/. However, communicating these addresses, as well as MAC addresses like 44:8f:7e:06:8c:ce, can be prone to errors for those who are not tech-savvy. Additionally, it does not provide any historical data, especially from previous occurrences of issues.
Navigating the World Wide Web
To access a web page, such as https://mayert.org, individuals initially connect to a DNS server to translate the host portion (mayert) and the Top Level Domain (org) of the URL into an IP address, such as 212.214.56.60. Every web request also includes the type of the computer and browser, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Understanding the Significance of Default Gateways
The default gateway is usually an address that is automatically configured via DHCP. This includes a default gateway, such as 172.18.144.165, which is where the computer sends all of its traffic to be routed onwards. For IPv6, detailed instructions on how to address connectivity issues can be found in our blog post: how-to-fix-ipv6-connectivity/. On Mac or Linux systems, this can be verified 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 172.18.144.165 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 fe80:3a3b:f961:cca0:da2c%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): {148.73.216.83, 172.221.158.126}
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 44:8f:7e:06:8c:ce
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:0a:1b:4c:c9:c9
}
Fixing Connectivity Issues: Wired vs Wireless
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you are running OSX/macOS version 10.14.6, 11.0.6, or 12.3.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a continuous set of related values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One immensely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose tool, which can generate a multitude of logs (although much of it is only relevant at a specific point in time, similar to wdutil).
To run it in the background and have it write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you want to run it interactively, you can use sudo /usr/bin/sysdiagnose, although there is limited interaction. 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. Just be cautious of the file sizes, which are approximately 300MB.
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P.S. Tips For Remote Network and Client Support
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