How To Test Mac No-access
The Functioning of Internet Addressing
When using the Internet, individuals may have a Public IPv4 address, such as 236.8.56.70, or an IPv6 address, such as 2000:3cd1:a60f:c7b:8044:acbe:1f08:a422. This information can be verified at https://test-ipv6.com/. Despite this, translating and referencing these addresses, as well as MAC addresses like c0:39:c9:83:d5:77, can be prone to errors and become complex, especially for those not well-versed in technology. Furthermore, it does not provide any historical data, particularly for previous issues.
Navigating through the Internet
When attempting to access a webpage such as https://hilpert-oreilly.co, the initial step involves contacting a DNS server to convert the host part (hilpert-oreilly) in combination with the Top Level Domain (co) of the URL to an IP address like 171.144.12.41. Every web request made by your computer and browser contains its version information. For example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Usually, the default gateway is an automatically configured address obtained via DHCP. A typical default gateway address might be 10.18.254.224 (although they usually end in .1 or .254 based on the scope size), and this is where your computer sends all its traffic to be directed further. For IPv6, more detailed information can be found in our article on how-to-fix-ipv6-connectivity/, or it can be verified on Mac or Linux using the following method:
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 10.18.254.224 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 fe80:75bb:76f7:a146:3f46%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): {154.34.223.248, 90.239.247.192}
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 c0:39:c9:83:d5:77
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:d2:8c:b3:4b:cc
}
Troubleshooting Connectivity on Apple Devices
When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Effective Solutions for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.2, 11.0.8, or 12.2.1, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that practice remote work and Work From Anywhere (WFA).
Useful Built-in Scripts for Troubleshooting
One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which offers a dump of current wireless-related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a comprehensive set of logs, although much of it is only related to wireless on a point-in-time basis, similar to wdutil.
To run sysdiagnose in the background and write logs to /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 the command 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. Keep in mind that the file sizes are approximately 300MB.
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