How To Test OSX Issues
Understanding the Function of Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 181.140.70.121 or an IPv6 address like 2000:8be0:9cc3:de38:d07:64b2:306e:9fe7. Verification of this assignment can be done at https://test-ipv6.com/. However, communicating these complex addresses, including MAC addresses like 1f:f0:af:dc:b3:cf, may pose challenges, especially for those with limited technical knowledge. Moreover, the lack of historical data further complicates matters, particularly when trying to address past issues.
Navigating Web Pages
Accessing a website like https://osinski-rolfson.com initially involves connecting to a DNS server to convert the host portion (osinski-rolfson) combined with the URL’s Top Level Domain (com) into an IP address, such as 153.143.225.141. With every web request, your computer and browser include details about their type, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
Understanding the Significance of Default Gateways
By default, your gateway is assigned an address through DHCP, typically ending in .1 or .254 depending on the scope size (e.g., 172.29.154.172), and serves as the location where your computer forwards all its traffic. While a detailed guide on configuring IPv6 can be found at how-to-fix-ipv6-connectivity/, you can verify this information on Mac or Linux systems.
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 172.29.154.172 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:c1cd:5983:7dae:748d%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): {116.28.38.171, 213.202.138.212}
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 1f:f0:af:dc:b3:cf
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 10:1e:02:26:a4:69
}
Resolving Issues with Wired and Wireless Connections
When it comes to transferring data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps for Troubleshooting on Apple macOS / OSX
Regardless of whether you are running OSX/macOS versions like 10.14.2, 11.0.6, or 12.1.9, there are various troubleshooting tools available. However, these manual methods and scripts do not provide a set of correlated values over time, which is where automated remote troubleshooting becomes essential, especially for teams engaged in remote work and Work From Anywhere (WFA).
Using In-Built Scripts for Assistance
A helpful 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 logs for troubleshooting. Alternatively, the sysdiagnose tool offers a more comprehensive option to generate a wide range of logs, although most are only point-in-time related to wireless, similar to wdutil.
You can run sudo nohup /usr/bin/sysdiagnose -u & to run it in the background, and it will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (even though there is not much interaction), you can use the command sudo /usr/bin/sysdiagnose and it will provide a privacy warning. When 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 locate the path. Be cautious of the file sizes, which are approximately 300MB more or less.
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