How Can I Check OSX Internet Connection
The Functioning of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address, such as 72.224.224.95, or an IPv6 address like 2000:b6ef:2e2b:53ee:405b:d497:d58a:5e0. This can be verified at https://test-ipv6.com/. However, communicating these addresses, or even referencing MAC addresses like 56:71:11:f7:55:0e, can be prone to errors and become complex, especially for those not well-versed in technology. Moreover, this method lacks the provision of historical data, especially pertaining to previous issues.
Navigating the Internet
Accessing a website like https://bergnaum-cassin.org involves an initial contact with a DNS server, which is responsible for converting the host component (bergnaum-cassin) in combination with the Top Level Domain (org) of the URL into an IP address, such as 156.65.56.176. Whenever a web request is made, your computer and browser also communicate their type, for instance 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
The default gateway is usually an address that is automatically configured through DHCP. It serves as the destination for all the traffic that your computer sends for further routing. Commonly, a default gateway is assigned, such as 192.168.197.120, with it typically ending in .1 or .254 depending on the scope size. Those wanting to explore more about IPv6 can refer to a comprehensive guide at: how-to-fix-ipv6-connectivity/. On a Mac or Linux system, the default gateway can be verified with 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 192.168.197.120 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 fe80:10b:8cac:751a:270a%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): {248.29.149.119, 122.155.136.179}
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 56:71:11:f7:55:0e
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 67:11:ce:f9:70:d6
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, the medium you use, whether wired or wireless (Wi-Fi), operates at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS version 10.12.5, 11.4.2, or 12.3.9, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that practice remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which provides a CLI dump of current wireless settings, and can also be configured to generate specific troubleshooting logs. Another comprehensive tool is the sysdiagnose tool, which can generate a range of logs, although most of it is only relevant to wireless issues similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, usesudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience, run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, allowing you to navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. However, be mindful of the file sizes, which can be around 300MB.
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