How Can I Test OSX Internet Connection
Understanding Internet Addressing
When you’re connected to the Internet, your device is assigned a unique identifying address. This might be a Public IPv4 address, such as 165.96.105.224, or an IPv6 address like 2000:ddab:e64d:ea53:d5a9:d8e3:6c:c54e. These addresses can be verified using tools like https://test-ipv6.com/. However, communicating these addresses and other network identifiers, such as MAC addresses like a8:42:e7:bc:80:73, can be tricky and error-prone, especially for those who aren’t tech-savvy.
Navigating the World Wide Web
When you want to visit a website, such as https://stamm.org, your device communicates with a Domain Name System (DNS) server to translate the website’s name into an IP address, like 89.49.165.215. Additionally, your computer and web browser transmit specific information with every web request, indicating the type of technology being used.
Understanding the Role of Default Gateways
The default gateway for your device is typically assigned automatically through Dynamic Host Configuration Protocol (DHCP). This gateway, often ending in .1 or .254, serves as the entry and exit point for all network traffic from your device. For troubleshooting and verification, similar processes can be used in both IPv6 and IPv4 environments.
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 172.27.131.120 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 fe80:6716:3a20:9590:b210%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): {147.89.236.96, 244.173.59.6}
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 a8:42:e7:bc:80:73
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 e9:68:f4:da:dd:c9
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.11.9, 11.1.2, or 12.0.2, 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 invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A very useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although the information is mostly point-in-time related to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. For interactive use, you can run sudo /usr/bin/sysdiagnose, which will display a privacy warning. If 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. However, be mindful of the file sizes, which are approximately 300MB.
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