How Can I Test Mac Issues
Understanding the Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 45.73.141.188 or an IPv6 address like 2000:c13c:b13e:4f0b:3445:8f82:d797:8be3. Verification of this information can be done at https://test-ipv6.com/. However, explaining these addresses to non-technical individuals, or mentioning MAC addresses like 66:dc:f6:12:5b:27, may lead to errors and complexity. Furthermore, there is no provision for historical data, especially pertaining to past issues.
Navigating the Internet
Accessing a website such as https://kuvalis-kreiger.com involves engaging a DNS server to convert the host section (kuvalis-kreiger) along with the Top Level Domain (com) of the URL, into an IP address like 253.122.55.65. Your computer and browser transmit their specifications with every web request, 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 Automated Gateways
Typically, your default gateway is an automatically configured address obtained via DHCP. The default gateway, such as 192.168.130.22 (usually ending in .1 or .254 based on the scope size), is where your computer directs all its traffic for onward routing. While a comprehensive guide on IPv6 can be found at how-to-fix-ipv6-connectivity/, checking on Mac or Linux involves:
command to check details
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 192.168.130.22 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:dfb:7b2a:ece2:e699%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): {48.122.78.137, 75.74.37.12}
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 66:dc:f6:12:5b:27
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 eb:89:fb:d6:40:38
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Addressing Problems on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.4, 11.2.3, or 12.0.4, there are multiple tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where the significance of automated remote troubleshooting becomes apparent, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to the wireless settings at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively by using sudo /usr/bin/sysdiagnose, which will open Finder in the correct location or allow you to navigate to /var/tmp. Keep in mind that the file sizes are approximately 300MB.
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