How To Check MacOS Internet Connection
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address, such as 237.173.150.227, or an IPv6 address, such as 2000:f39e:7b35:ea3:9314:f005:f3d9:ac22. You can verify this by visiting https://test-ipv6.com/. However, for those who are not tech-savvy, conveying these addresses, or even referencing MAC addresses like 32:1b:ce:8a:ee:d5, can be prone to mistakes and can become complex quickly. Moreover, this method does not provide any historical data, particularly when dealing with past issues.
Navigating the World Wide Web
When attempting to access a webpage, such as https://schulist.com, your computer initially reaches out to a DNS server to convert the host portion (schulist) along with the Top Level Domain (com) of the URL into an IP address like 129.182.73.226. Furthermore, your computer and browser disclose its type with every web request, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway is typically an automatically assigned address via DHCP. You are provided with a default gateway, such as 172.20.112.200 (although they generally end in .1 or .254 based on the scope size), and this is where your computer directs all of its traffic to be routed further. For IPv6, a more detailed explanation is available in the article how-to-fix-ipv6-connectivity/, but you can also verify this on Mac or Linux 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 172.20.112.200 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 fe80:5030:7a6b:2fc0:cd93%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): {56.237.72.107, 209.225.22.224}
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 32:1b:ce:8a:ee:d5
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 9e:23:fa:4b:ef:d5
}
Addressing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be utilizing either a wired or a wireless (Wi-Fi) medium operating at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Irrespective of the version of OSX/macOS you are using, whether it’s 10.13.4, 11.3.4, or 12.2.8, there are a variety of tools available for fixing connectivity issues. However, the manual actions and scripts only offer fragmented data and do not provide a comprehensive overview. This is where automated remote troubleshooting comes in, especially for teams following a remote work setup and embracing the Work From Anywhere (WFA) approach.
Utilizing In-Built Scripts for Assistance
An extremely valuable tool for troubleshooting on OSX/macOS is sudo wdutil info, which presents a detailed dump of the current wireless settings through the CLI, and can also be configured to generate specific logs for resolving issues. Furthermore, for a more comprehensive approach, the sysdiagnose tool can be used to generate a wide range of logs (although these are mostly related to wireless and are only reflective of a specific point in time, much like wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and produce logs in /var/tmp/<blah>.tar.gz for analysis. If you prefer an interactive run (even though there isn’t much interactivity involved), you can execute sudo /usr/bin/sysdiagnose and a privacy warning will be displayed. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G. It’s important to be mindful of the file sizes, which are approximately 300MB.
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