How To Check Mac Internet
Demystifying Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 34.240.147.8 or an IPv6 address like 2000:c43a:1b83:80f3:60ac:4914:e458:a25b. A visit to https://test-ipv6.com/ can confirm this. However, relaying these addresses or MAC addresses such as d8:d0:93:2e:06:8d can be prone to errors and become complex, especially for those unfamiliar with technical jargon. Furthermore, there is a lack of historical data, particularly when trying to resolve past issues.
Navigating the World Wide Web
To access a website like https://veum.com, the initial step involves interacting with a DNS server to convert the host portion (veum) and Top Level Domain (com) of the URL to an IP address, for example, 177.221.224.186. Whenever your computer and browser make web requests, they also transmit the browser type, such as:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
The default gateway is commonly assigned automatically through DHCP. A typical default gateway might be 172.25.210.227 (often ending in .1 or .254 based on the scope size) to which your computer directs all its traffic for onward routing. For those interested in IPv6, a detailed guide is available at how-to-fix-ipv6-connectivity/, while Mac or Linux users can verify it 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 172.25.210.227 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 fe80:99bc:e5cf:a244:878c%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): {195.75.146.142, 189.169.144.191}
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 d8:d0:93:2e:06:8d
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 94:2b:17:77:de:07
}
Resolve Network Connectivity Issues for Wired and Wireless Connections
When it comes to transmitting data, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer to route the data to your router.
Steps for Troubleshooting on Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.11.9, 11.6.2, or 12.1.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI, and can also be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use sudo /usr/bin/sysdiagnose and heed the 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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