How Can I Troubleshoot Apple Connectivity
Explanation of Internet Addressing Mechanism
When connecting to the internet, you are assigned a Public IPv4 address such as 72.157.248.235 or an IPv6 address like 2000:9843:6a44:36d4:2ffb:4cf9:d45c:e424. This information can be verified at https://test-ipv6.com/. Communicating these addresses, as well as MAC addresses such as 6d:14:b1:d9:3a:97, can be complex and error-prone, especially for non-technical individuals. Furthermore, this method lacks historical data, particularly when troubleshooting past issues.
Navigating the World Wide Web
In order to access a website, like https://auer.info, your computer initially communicates with a DNS server to convert the host portion (auer) combined with the Top Level Domain (.info) of the URL into an IP address, such as 30.7.46.13. All web requests from your computer and browser contain their type, for example Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0.
Significance of Default Gateways
Typically, your default gateway is automatically configured through DHCP and you are allocated an address such as 172.17.183.95 (usually ending in .1 or .254 depending on the scope size). This default gateway is where your computer directs all its traffic for further routing. For IPv6, a detailed guide exists on how-to-fix-ipv6-connectivity/, but you can also verify it 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 172.17.183.95 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 fe80:200d:3795:8433:c79b%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): {22.168.138.19, 146.46.239.158}
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 6d:14:b1:d9:3a:97
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 07:92:52:99:69:1a
}
How to Resolve Issues with Wired and Wireless Connections
When it comes to transferring data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Take on Apple macOS / OSX
Regardless of whether you are on OSX/macOS version 10.15.1, 11.3.2, or 12.2.5, there are various troubleshooting tools available. However, manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Pre-installed Scripts That Offer Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless 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 for you. If you prefer to run it interactively (although there is not much interaction), you can use the commandsudo /usr/bin/sysdiagnose, which 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 or use Finder with Cmd+Shift+G to point Finder to the path. Keep in mind the file sizes are approximately 300MB.
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