How Do You Test Apple Issues
Understanding Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 or an IPv6 address. Identifying these addresses can be done by visiting https://test-ipv6.com/ to check for their presence. However, effectively communicating these addresses, as well as MAC addresses, can be challenging for those who are not technologically inclined. Moreover, these addresses do not provide historical data, especially from past issues.
Navigating the World Wide Web
Accessing a website, such as https://cummings-barton.info, begins with contacting a DNS server to translate the host portion of the URL, along with the Top Level Domain, into an IP address. When making web requests, your computer and browser send information about their type, such as Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
The Significance of Default Gateways
By default, a gateway gets automatically configured via DHCP, resulting in an assigned address such as 10.13.19.15. Typically, these addresses end in .1 or .254, depending on the scope size. This is where all your computer’s traffic gets routed for further processing. For those interested in troubleshooting IPv6 connectivity on Mac or Linux, a detailed guide is available at how-to-fix-ipv6-connectivity/.
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 10.13.19.15 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 fe80:6300:d752:5d74:58da%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): {133.185.193.40, 192.37.94.90}
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 e8:d5:31:28:e9:80
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 ab:7a:ce:f6:58:f4
}
Resolve Issues with Wired or Wireless Connections
When it comes to sending data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Action Plan for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS version 10.12.4, 11.1.2, or 12.3.3, there are various troubleshooting tools available. 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 that adopt remote work and Work From Anywhere (WFA) practices.
Useful Built-in Scripts
One useful tool for OSX/macOS users is sudo wdutil info, which provides a dump of current wireless-related settings to the Command Line Interface (CLI). It can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many are only relevant to wireless settings at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose and it 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 manually, or use Finder with Cmd+Shift+G to navigate to the path. Keep in mind that the file sizes are approximately 300MB.
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