How To Test MacOS Internet
Demystifying Internet Addressing
When navigating the Internet, you are assigned a Public IPv4 address, such as 65.195.108.128, or an IPv6 address, such as 2000:1fd7:92e2:9489:2716:c8cf:84b4:a387. You can verify this information using the tool provided by https://test-ipv6.com/. Communicating these addresses with those who are not tech-savvy, or even mentioning MAC addresses like 65:19:6e:7b:83:23, can be prone to error and quickly become convoluted. Furthermore, it does not offer any historical data, especially related to past issues.
Navigating the World Wide Web
Accessing a webpage, such as https://dicki.biz, involves an initial connection to a DNS server in order to translate the host portion (dicki) combined with the Top-Level Domain (biz) of the URL into an IP address, for example, 234.184.26.175. Your computer and browser send its type along with all web requests, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP, such as 172.16.60.130 (although they usually end in .1 or .254 based on the scope size). This is the point to which your computer sends all its traffic to be further routed. For IPv6, a comprehensive guide on how-to-fix-ipv6-connectivity/ is available, and you can 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 172.16.60.130 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:d2c2:cf7f:c493:6b3%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): {73.101.167.126, 249.50.42.37}
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 65:19:6e:7b:83:23
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 e0:48:33:c2:13:09
}
Resolving Issues with Wired and Wireless Connections
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.
Troubleshooting Tips for Apple macOS / OSX
Irrespective of whether you are running OSX/macOS version 10.11.6, 11.4.4, or 12.2.8, there are several troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly beneficial, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts
One 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 pertains only to a specific point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (even though there is not much interaction), you can executesudo /usr/bin/sysdiagnose, which will display 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. However, be cautious of the file sizes, which are typically around 300MB.
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