How To Support Apple Connectivity
The Functioning of Internet Addressing
When using the Internet, you will have a unique IPv4 address like 153.44.188.86 or an IPv6 address like 2000:982:903f:7b1c:5140:ee17:ba6e:a038. These can be verified at https://test-ipv6.com/. Communicating or referencing these addresses, or even mentioning MAC addresses like a1:05:c7:6f:43:22, can be prone to errors and quickly become complex, especially for non-technical individuals. Moreover, this method does not provide any historical data, particularly for past issues.
Navigating the World Wide Web
To access a website such as https://batz-thompson.co, you must first contact a DNS server to convert the host part (batz-thompson) in combination with the Top Level Domain (co) of the URL into an IP address like 72.157.138.200. Your computer and browser send their types with all web requests, for example, Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Your default gateway is typically an automatically configured address through DHCP. You receive a default gateway like 10.140.73.157 (although they generally end in .1 or .254 depending on the scope size) and this is where your computer forwards all its traffic for further routing. For IPv6, detailed instructions can be found on how-to-fix-ipv6-connectivity/ but it can be verified on Mac or Linux using the following command:
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 10.140.73.157 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:d79:cfc8:23a1:9a71%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): {115.249.70.0, 120.253.123.57}
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 a1:05:c7:6f:43:22
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 85:42:1a:eb:48:e4
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to sending data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layers.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you’re running - whether it’s 10.12.4, 11.2.6, or 12.2.8 - there are various tools available for troubleshooting connectivity issues. However, these manual actions and scripts don’t provide a set of correlated values over time, making automated remote troubleshooting particularly useful for remote work and Work From Anywhere (WFA) scenarios.
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the Command Line Interface (CLI) and can also generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. For an interactive version, you can runsudo /usr/bin/sysdiagnose, which will display 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. Keep in mind that file sizes are approximately 300MB.
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