How Can I Check MacOS Internet Connection
The Functioning of Internet Addressing
When using the Internet, it is possible to obtain a Public IPv4 address, such as 166.55.221.95, or an IPv6 address, like 2000:41cd:5810:3330:c97a:e163:d2f7:3e6f. Verification can be done through https://test-ipv6.com/. Communicating these addresses, or even referring to MAC addresses such as 14:08:cf:2b:86:4f, can be prone to errors and complex, especially for individuals who are not well-versed in technology. Furthermore, this method does not provide any historical data, particularly regarding past issues.
Navigating the World Wide Web
To access a webpage like https://fadel.biz, the initial step is to contact a DNS server to convert the combination of the host portion (fadel) and the Top Level Domain (biz) of the URL into an IP address, such as 132.140.97.222. Upon making web requests, your computer and browser transmit your type, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
The Significance of Default Gateways
Generally, a default gateway is an address that is automatically configured via DHCP. It usually takes the form of 192.0.0.102 (though typically ending in .1 or .254 based on the scope size), and it is the point to which your computer sends all its traffic for further routing. Information on fixing IPv6 connectivity is available in-depth at how-to-fix-ipv6-connectivity/, and confirmation can be done on Mac or Linux by 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 192.0.0.102 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:dd44:4b6:7160:8df2%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): {60.182.66.42, 164.77.138.131}
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 14:08:cf:2b:86:4f
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 4c:ff:a3:8f:4e:40
}
Solve Network Connection Issues for Wired and Wireless Setups
When it comes to sending data to your router, you might be using a wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Resolving Connectivity Problems on Apple macOS / OSX
Regardless of whether you are using OSX or macOS versions like 10.11.1, 11.0.7, or 12.1.2, there are various troubleshooting tools available. However, these manual actions and scripts fail to provide a set of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Leverage Pre-installed Scripts for Assistance
An extremely useful tool on OSX/macOS is sudo wdutil info, which displays the current wireless settings in the CLI and can be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool provides a comprehensive set of logs (although most of it is point-in-time information related to wireless, like wdutil).
To run it in the background and generate logs, use the command sudo nohup /usr/bin/sysdiagnose -u &, which will write logs to /var/tmp/<blah>.tar.gz. Alternatively, to run it interactively, use sudo /usr/bin/sysdiagnose and it will give 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 Cmd+Shift+G in Finder. Keep in mind that the file sizes are around 300MB.
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