How Can I Check MacOS Internet
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 64.41.101.205 or an IPv6 address like 2000:17fe:4b2b:b950:568b:5a93:5810:3edd. To verify your assigned address, you can visit https://test-ipv6.com/. However, for those who aren’t familiar with technical terms, communicating or memorizing these addresses can be prone to errors and can become complicated quickly. It also does not provide any historical data, especially when encountering recurring issues.
Navigating the World Wide Web
In order to access a website, such as https://gerhold.net, your computer contacts a DNS server to convert the host portion (gerhold) along with the Top Level Domain (net) of the URL into an IP address like 234.172.95.105. Each web request also includes information about the browser and computer, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
By default, your computer is assigned a default gateway through DHCP, often ending in .1 or .254 based on the scope size, such as 10.41.232.75. This default gateway is responsible for routing all outgoing traffic from your computer. For a more detailed explanation on IPv6, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify this configuration by using:
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 10.41.232.75 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 fe80:9fbb:ff96:409b:4f00%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): {47.67.216.171, 98.95.206.21}
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 93:c4:e3:ca:5a:5f
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 f8:55:a9:06:c3:52
}
Fixing Network Connectivity Issues
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Technical Troubles on Apple macOS / OSX
No matter which version of OSX/macOS you are currently using, whether it’s 10.13.6, 11.5.5, or 12.0.9, there are various tools available for troubleshooting. However, the manual actions and scripts provided do not offer a consistent set of correlated values over time. This is where automated remote troubleshooting becomes extremely useful, especially for teams that are in favor of remote work and Work From Anywhere (WFA).
Utilizing In-Built Scripts for Assistance
One extremely 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 be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although many are only relevant to the current wireless setup, similar to wdutil.
To run it in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will prompt 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 Finder with Cmd+Shift+G or by manually entering the path. Keep in mind that the file sizes are approximately 300MB or so.
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