How To Test MacOS Internet Connection
Understanding Internet Addressing
When using the Internet, you are assigned a unique Public IPv4 or IPv6 address, such as 237.32.187.209 or 2000:a92d:3bbd:cfdf:55ca:7af3:9de:b6e5. You can verify your address at https://test-ipv6.com/. However, effectively communicating these addresses, as well as MAC addresses like 03:a4:bb:5c:dc:ba, can be challenging, especially for non-technical individuals. Moreover, this method lacks historical data, making it difficult to troubleshoot previous problems.
Navigating the World Wide Web
When accessing a website, such as https://durgan.net, your computer first contacts a DNS server to translate the URL’s host portion (durgan) and Top Level Domain (net) to an IP address like 47.172.180.128. Additionally, your computer and browser send their type with every web request, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).
The Significance of Default Gateways
Typically assigned automatically via DHCP, your default gateway, like 172.18.105.32 (often ending in .1 or .254 based on the scope size), is where your computer sends all of its traffic to be routed onwards. For those interested in IPv6, a detailed guide on how-to-fix-ipv6-connectivity/ is available for Mac or Linux users to check.
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 172.18.105.32 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:d8c6:86a7:cd9b:bc33%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): {111.211.4.93, 6.82.244.68}
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 03:a4:bb:5c:dc:ba
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 f9:6a:3d:56:8c:0a
}
Solving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX or macOS you are running, whether it’s 10.15.5, 11.0.4, or 12.2.7, 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 essential, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One incredibly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it only provides point-in-time information related to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will display a privacy warning. 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 to find the path. Keep in mind that the file sizes are around 300MB more or less.
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 🏠🏝🛰.
