How Can I Check OSX No-access
Understanding Internet Addressing
When connecting to the Internet, you may be assigned a Public IPv4 address such as 132.23.220.92 or an IPv6 address like 2000:9bfe:da64:e6c9:e8a8:1a36:8d54:2eb7. A convenient way to verify this is by visiting https://test-ipv6.com/. However, communicating these addresses, or even referencing MAC addresses like 52:73:ea:0f:94:87, can become complicated for those not well-versed in technology. Furthermore, this approach does not provide any historical information, particularly when addressing past issues.
Navigating the World Wide Web
When attempting to access a website, such as https://fisher.net, the first step is to contact a DNS server to convert the combination of the host portion (fisher) and the Top Level Domain (net) of the URL into an IP address, like 196.137.47.30. Every web request from your computer and web browser actually includes the 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
Typically, your default gateway is automatically assigned through DHCP. This results in a default gateway, such as 172.21.170.33 (usually ending in .1 or .254 depending on the scope size), to which your computer directs all of its traffic for onward routing. For IPv6, detailed instructions are available in our thorough examination of how-to-fix-ipv6-connectivity/, or you can refer to Mac or Linux for verification 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 172.21.170.33 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 fe80:4d3b:58d4:6764:1c9%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): {130.241.57.77, 78.62.206.49}
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 52:73:ea:0f:94:87
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 e1:34:03:53:33:4b
}
Repairing Network Connections
In order to transmit data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps for Addressing Issues on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.7, 11.6.5, or 12.3.6, there are various troubleshooting tools available. However, manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes especially valuable, particularly for teams that have embraced remote work and Work From Anywhere (WFA).
Utilizing Pre-Installed Scripts for Assistance
A very useful tool on OSX/macOS is sudo wdutil info, which delivers a dump to the CLI of current wireless related settings. This can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide array of logs, although much of it is only relevant to wireless at specific points in time, similar to wdutil.
To run the sysdiagnose tool 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 prefer to run it interactively (even though there is minimal interaction), you can execute sudo /usr/bin/sysdiagnose and it will display 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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