Test OSX Connectivity
Understanding How Internet Addressing Functions
When using the Internet, you are assigned a Public IPv4 address such as 149.61.184.175 or an IPv6 address like 2000:eaac:1e77:4b76:4227:8794:b475:3cf4. You can verify this by visiting https://test-ipv6.com/. However, conveying these addresses, and even mentioning MAC addresses like ce:fe:b1:d8:0b:19, can be error-prone and complex, particularly for individuals who are not well-versed in technology. Moreover, this approach does not provide any historical data, especially from past issues.
Navigating the World Wide Web
In order to access a website such as https://rolfson.biz, you initially communicate with a DNS server to convert the host part (rolfson) in combination with the Top Level Domain (biz) of the URL into an IP address like 91.27.10.91. Whenever your computer and browser make web requests, they actually include their type, for instance:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Significance of Default Gateways
Your default gateway is typically an automatically configured address through DHCP. This default gateway, such as 10.148.194.161 (although they typically end in .1 or .254 depending on the scope size), is where your computer forwards all its traffic to be routed onwards. For IPv6, a comprehensive guide on how to fix IPv6 connectivity is available, but you can also verify this on Mac or Linux using the following command:
ifconfig
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 10.148.194.161 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 fe80:1e4c:d90e:8c33:94fe%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): {35.51.121.184, 231.108.112.13}
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 ce:fe:b1:d8:0b:19
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 33:0c:5f:14:fe:fd
}
Resolving Issues with Wired or Wireless Connections
When transmitting data to your router, you may be utilizing 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/macOS you are running, whether it’s 10.12.4, 11.3.7, or 12.2.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams adapting to remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose, which can generate a variety of logs related to wireless issues.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, running sudo /usr/bin/sysdiagnose interactively will provide a privacy warning and open Finder in the correct location. The file sizes are typically around 300MB.
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