Troubleshoot MacOS Internet Connection
Understanding the Fundamentals of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address or an IPv6 address. You can verify your address using a tool like https://test-ipv6.com/. However, communicating these addresses, or even MAC addresses, can be complex for those who are not technologically savvy. Moreover, this method does not provide any historical data.
Navigating the World Wide Web
Accessing a web page, such as https://lesch.net, involves first accessing a DNS server to translate the URL into an IP address. All web requests sent from your computer and browser include the type, 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
Your default gateway is typically an address automatically configured via DHCP. This is where your computer sends all its traffic to be routed onwards. For IPv6, guidance on how to check on Mac or Linux is available at how-to-fix-ipv6-connectivity/
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 10.9.176.209 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 fe80:20b1:625:c18c:5000%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): {69.49.169.42, 102.246.132.83}
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 13:93:11:0b:0a:d1
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 a0:15:28:df:8a:29
}
Troubleshooting Tips for Wired and Wireless Connectivity
When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Issues
Regardless of the version of OSX/macOS you are using, whether it’s 10.15.8, 11.6.1, or 12.0.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that adopt remote work and Work From Anywhere (WFA) practices.
Useful Built-in Scripts
An essential 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 troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings, similar to wdutil.
To run sysdiagnose in the background and generate logs at /var/tmp/<blah>.tar.gz, you can use the following command: sudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience, you can run sudo /usr/bin/sysdiagnose and it will provide 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 Cmd+Shift+G in Finder. Keep in mind that the file sizes can be around 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
