How Can I Test OSX Connectivity
Understanding Internet Protocol Addressing
When using the Internet, individuals typically have either a Public IPv4 or IPv6 address. You can verify this by visiting https://test-ipv6.com/. However, communicating these addresses, such as MAC addresses, can be challenging for those not well-versed in technology. Furthermore, this method does not provide any historical data, particularly when addressing past issues.
Navigating the World Wide Web
Accessing a website like https://denesik.net involves first contacting a DNS server to convert the URL’s host and Top Level Domain to an IP address, such as 64.189.80.178. Every web request from your computer and browser includes its type, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
The default gateway is typically assigned automatically through DHCP and usually ends in .1 or .254. This is where all of your computer’s traffic is sent for further routing. For IPv6, more information is available in our in-depth article on how-to-fix-ipv6-connectivity/, or you can check 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 192.0.0.177 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 fe80:452a:73b2:25c4:2d4e%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): {152.63.236.152, 149.66.124.187}
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 3e:c0:7a:6e:8f:50
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 fd:14:3c:ba:69:0a
}
Resolving Connectivity Issues in Wired or Wireless Networks
When it comes to transmitting data to your router, you may be using a wired connection or a wireless (Wi-Fi) network at the physical and data layer.
Tips and Tricks for Apple macOS / OSX Users
Regardless of whether you are using OSX or macOS versions such as 10.12.6, 11.1.4, or 12.2.5, there are various tools available for troubleshooting connectivity issues. However, these manual actions and scripts do not provide a consistent set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are engaged in remote work and Work From Anywhere (WFA).
Useful Built-in Utilities
One of the most useful tools on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings in the CLI and can also be configured to generate specific logs for troubleshooting purposes. Another comprehensive tool is the sysdiagnose utility, which can be used to generate a wide range of logs, although most of the information related to wireless is only relevant at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /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. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder or use Cmd+Shift+G to point Finder to the path. Keep in mind that the file sizes are approximately 300MB.
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