How To Troubleshoot Apple Internet Connection
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 or IPv6 address, which can be verified from a website like https://test-ipv6.com/. However, the complexity of conveying and managing these addresses, as well as MAC addresses, can pose challenges, especially for non-technical individuals.
Navigating the World Wide Web
Accessing a website, such as https://koss.name, involves using a DNS server to translate the URL’s host portion and Top Level Domain to an IP address, like 143.100.15.66. Every web request from your computer and browser contains specific information about its type.
Significance of Default Gateways
The default gateway, typically assigned through DHCP, serves as the destination for all outgoing traffic from your computer. In the case of IPv6, detailed instructions on diagnosis and resolution can be found on how-to-fix-ipv6-connectivity/. On Mac or Linux systems, the default gateway can be checked using specific commands.
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 192.168.60.199 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 fe80:15c2:8947:2969:8f1f%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): {106.109.111.245, 9.153.84.60}
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 08:4b:cf:e6:25:ca
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 c7:02:30:a0:ed:1e
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you’re using, whether it’s 10.14.2, 11.2.5, or 12.2.1, there are several tools available for troubleshooting. However, these manual actions and scripts don’t provide a set of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that promote remote work and Work From Anywhere (WFA).
Helpful Built-in Scripts
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 also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a variety of logs (although many are specific to a moment in time in relation to wireless, similar to wdutil).
By running sudo nohup /usr/bin/sysdiagnose -u & in the background, logs will be written to /var/tmp/<blah>.tar.gz. Running it interactively (although there is limited interaction) can be done by running sudo /usr/bin/sysdiagnose, which will prompt 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 Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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