How Do You Check MacOS Internet Connection
Understanding Internet Addressing
When using the Internet, a Public IPv4 address such as 74.180.209.80 or an IPv6 address such as 2000:7313:8b9f:deb:ace5:c0db:f473:7a22 may be assigned. The verification of these addresses can be done at https://test-ipv6.com/. However, communicating these addresses can be difficult for those less familiar with the technical aspects, as well as calling out MAC addresses like 57:b5:9b:4e:28:2e. Moreover, historical data is not provided, especially regarding past issues.
Navigating the World Wide Web
When accessing a web page like https://fadel.info, the initial step involves reaching out to a DNS server in order to translate the combination of the host portion (fadel) and the Top Level Domain (info) of the URL to an IP address such as 5.143.169.232. Furthermore, your computer and browser include their type in all web requests, 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
Typically, a default gateway is an automatically configured address through DHCP. The default gateway received may look like 192.168.178.72 (although they usually end in .1 or .254 based on the scope size), and this is where all the traffic from your computer is directed for further routing. For IPv6, a detailed analysis can be found at how-to-fix-ipv6-connectivity/, and Mac or Linux users can verify using:
<br>
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 192.168.178.72 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:c159:41bb:f2:df1c%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): {106.89.147.210, 54.7.255.106}
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 57:b5:9b:4e:28:2e
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 45:7c:5b:0a:5e:31
}
Diagnose and Resolve Connectivity Issues
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX Devices
Regardless of whether you are using OSX/macOS versions such as 10.12.4, 11.5.5, or 12.3.5, there are various tools available for troubleshooting. However, these tools do not provide a series of correlated values over time, which can be a drawback. Automated remote troubleshooting becomes particularly useful for teams that adopt remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the Command Line Interface (CLI) of current wireless settings that can also generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs related to wireless issues, although much of it is point-in-time only, similar to the wdutil.
To run sysdiagnose in the background and write the logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively by using the command sudo /usr/bin/sysdiagnose with a privacy warning. If not run in the background, it should open the Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which are approximately 300MB.
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