How Can I Test Apple Issues
Understanding Internet Address Allocation
When connected to the Internet, you will have a unique Public IPv4 address, such as 172.191.187.107, or an IPv6 address like 2000:518:fb94:2058:dae2:a755:f587:926a. Verifying this can be done by visiting https://test-ipv6.com/. However, translating and communicating these addresses, and even mentioning MAC addresses like 7e:3b:f5:42:5d:b4, can become complex and error-prone for those who are not technology-savvy. Moreover, it does not provide any historical data, particularly during previous incidents.
Navigating the World Wide Web
When attempting to visit a web page such as https://turner.net, the first step involves accessing a DNS server to convert the host portion (turner) in combination with the Top Level Domain (net) of the URL into an IP address like 71.150.116.0. A computer and browser send their type with every web request, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
Typically, a default gateway is an automatically configured address obtained through DHCP. The default gateway, such as 172.23.252.20 (which typically ends in .1 or .254 based on the scope size), serves as the point where a computer forwards all its traffic for onward routing. For IPv6, a detailed explanation can be found at how-to-fix-ipv6-connectivity/. Additionally, Mac or Linux users can check this using the following method:
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 172.23.252.20 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 fe80:70d9:3b3c:c251:8112%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): {39.26.162.154, 89.126.205.236}
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 7e:3b:f5:42:5d:b4
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 23:94:a3:92:40:da
}
Resolving Connectivity Issues in Wired and Wireless Networks
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Irrespective of the version of OSX/macOS you are using - whether it’s 10.11.9, 11.4.3, or 12.0.7 - there are various tools available for resolving connectivity issues. However, these tools do not provide a series of correlated values over time, and this is where automated remote troubleshooting becomes vital, particularly for teams that have embraced remote work and the Work From Anywhere (WFA) concept.
In-Built Utilities for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate logs for troubleshooting purposes. Furthermore, the sysdiagnose tool offers a more comprehensive range of logs, although many of them are only point-in-time in terms of wireless issues, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. Alternatively, you can run it interactively with 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 Cmd+Shift+G in Finder. Be mindful of the file sizes, which are approximately 300MB.
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