How Can I Troubleshoot MacOS Internet Connection

Understanding the Functioning of Internet Addressing When using the internet, you may receive a Public IPv4 address, such as 186.30.145.25, or an IPv6 address, such as 2000:f5e4:246:2b50:3bcb:98e:7b54:350a. It is possible to verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to those unfamiliar with technology, or even mentioning MAC addresses like cd:d7:7a:34:5c:35, can lead to errors and complexity. Understanding the Functioning of Internet Addressing When using the internet, you may receive a Public IPv4 address, such as 186.30.145.25, or an IPv6 address, such as 2000:f5e4:246:2b50:3bcb:98e:7b54:350a. It is possible to verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to those unfamiliar with technology, or even mentioning MAC addresses like cd:d7:7a:34:5c:35, can lead to errors and complexity.

Understanding the Functioning of Internet Addressing

When using the internet, you may receive a Public IPv4 address, such as 186.30.145.25, or an IPv6 address, such as 2000:f5e4:246:2b50:3bcb:98e:7b54:350a. It is possible to verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to those unfamiliar with technology, or even mentioning MAC addresses like cd:d7:7a:34:5c:35, can lead to errors and complexity. Moreover, this method does not provide any historical data, particularly regarding past issues.

In order to reach a webpage, such as https://wisoky.com, you initially connect to a DNS server to convert the combination of the host portion (wisoky) and the Top Level Domain (com) of the URL into an IP address, such as 86.35.218.224. The computer and browser include their information with every web request, for example:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A

Significance of Default Gateways

Typically, your default gateway is an automatically assigned address through DHCP. The default gateway, such as 192.168.136.27 (usually ending in .1 or .254 based on the scope size), is where your computer directs all traffic to be routed. For IPv6, a comprehensive guide is available on how-to-fix-ipv6-connectivity/, and you can verify this on Mac or Linux using 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  192.168.136.27    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:abed:71f7:15ef:b86a%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): {86.67.22.237, 101.184.49.182}
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 cd:d7:7a:34:5c:35
  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 f0:d2:0c:b5:37:b8
}

Repairing Connectivity Issues with Wired and Wireless Networks

When it comes to transmitting data to your router, you might be utilizing either a wired or wireless (Wi-Fi) connection at the physical and data layer.

Troubleshooting Techniques for Apple’s macOS / OSX Operating Systems

Regardless of whether you are running OSX or macOS, whether it’s version 10.12.7, 11.6.5, or 12.1.4, there are a variety of troubleshooting tools available. However, these manual troubleshooting actions and scripts do not provide a set of correlated values over a period of time, which is where automated remote troubleshooting becomes valuable. This is particularly beneficial for teams that have adopted remote work and a Work From Anywhere (WFA) policy.

Utilizing Pre-Installed Scripts for Assistance

One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the command line interface and can also be configured to generate specific logs for troubleshooting purposes. In addition, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is only relevant to the wireless connection at a specific point in time, similar to wdutil.

To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, you can 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, although it will display a privacy warning. Running it in the background should open Finder in the correct location, or you can navigate to /var/tmp, or use Finder with Cmd+Shift+G to navigate to the path. However, be aware that the file sizes can be around 300MB more or less.

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