How Can I Support Apple Issues
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 168.177.98.5 or an IPv6 address like 2000:9690:f71f:8cb6:372b:84fe:dbbc:99f4. You can verify this information by visiting https://test-ipv6.com/. However, explaining and sharing these addresses with non-technical individuals, or even mentioning MAC addresses like f5:b1:46:9b:45:96, can be prone to errors and quickly become complex. Furthermore, this does not provide any historical data, especially when previous issues occurred.
Navigating the World Wide Web
When attempting to access a web page, for example, https://prosacco.com, you first connect to a DNS server to translate the host part (prosacco) along with the Top Level Domain (com) of the URL into an IP address like 93.13.243.20. Your computer and browser send their type along with all web requests, such as
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0.
The Significance of Default Gateways
Your default gateway is usually an automatically configured address via DHCP. The default gateway, such as 10.54.190.160 (although it typically ends in .1 or .254 depending on the scope size), is where your computer sends all its traffic to be routed onwards. For IPv6, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/, but you can also check on Mac or Linux using:
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 10.54.190.160 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 fe80:193d:75ec:4445:3616%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): {48.178.53.81, 126.253.1.40}
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 f5:b1:46:9b:45:96
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 8f:ad:8d:94:76:2b
}
Resolve Wired or Wireless Connectivity Issues
When it comes to the physical and data layer, you may be utilizing either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting Techniques for Apple macOS / OSX
Regardless of the version of OSX/macOS you are operating on, whether it’s 10.14.9, 11.4.1, or 12.0.7, there are various tools available for addressing connectivity issues. However, manual actions and scripts fail to provide a series of correlated values over time. This is where automated remote troubleshooting proves to be beneficial, especially for teams embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One particularly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless settings, and can also be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. Alternatively, running sudo /usr/bin/sysdiagnose interactively (though there isn’t much interaction) will prompt a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which are typically around 300MB.
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