How Do You Troubleshoot Apple Internet Connection
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address (e.g. 20.46.171.222) or an IPv6 address (e.g. 2000:d6a8:30ff:abdb:ab38:ef0c:7957:d0d). You can verify this at https://test-ipv6.com/. Communicating and managing these addresses, as well as MAC addresses like 44:be:ce:12:2d:57, can be complex and error-prone, especially for those who are not technologically inclined. Furthermore, there is no historical data available for previous occurrences of problems.
Navigating Through the Web
When accessing a web page such as https://prohaska-hoppe.io, your request goes to a DNS server to translate the host portion (prohaska-hoppe) along with the Top Level Domain (io) of the URL to an IP address like 222.112.123.68. Your computer and browser also send their type with all web requests, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
The Significance of Default Gateways
A default gateway is typically an automatically configured address through DHCP. It is the designated endpoint, such as 10.127.196.86, where your computer sends all of its traffic to be routed onward. For IPv6 connectivity troubleshooting, there is an in-depth guide available at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can check this by:
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 10.127.196.86 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:d450:eb55:c7ab:316b%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): {60.140.64.191, 12.125.6.124}
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 44:be:ce:12:2d:57
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 d3:06:10:96:20:f4
}
Resolving Connectivity Issues for Wired and Wireless Networks
When transmitting data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Effective Methods for Troubleshooting on Apple macOS / OSX
Regardless of the version of OSX/macOS you are operating on, whether it’s 10.12.8, 11.3.3, or 12.0.4, there are various tools available for troubleshooting. However, manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams engaged in remote work and the Work From Anywhere (WFA) approach.
Utilizing In-Built Scripts for Assistance
A highly beneficial tool on OSX/macOS is the sudo wdutil info command, which generates a dump of current wireless settings to the CLI and can also be configured to produce specific logs for troubleshooting. Furthermore, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
To run it in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (although there isn’t much interaction), you can execute the command sudo /usr/bin/sysdiagnose, which will result in a privacy warning. When 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 direct Finder to the path. Keep in mind that the file sizes are approximately 300MB, more or less.
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