How Do You Troubleshoot Apple Internet
How Internet Addressing Functions
In the realm of the Internet, one might acquire a Public IPv4 address such as 239.240.227.174 or an IPv6 address like 2000:3c2d:981b:c574:8968:854f:2f02:5184. Verification of this can be done via https://test-ipv6.com/. However, attempting to convey these addresses to those who are not technologically inclined, or even articulating MAC addresses like c0:6b:a7:3b:00:fe, can be prone to errors and become complicated rather quickly. Furthermore, this approach fails to provide any historical data, especially when dealing with past issues.
Navigating the World Wide Web
When accessing a webpage, such as https://kris.io, the initial step is to contact a DNS server to convert the combination of the host portion (kris) with the Top Level Domain (io) of the URL into an IP address like 244.59.189.233. Interestingly, the computer and browser transmit their type with every web request, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Predefined Gateways
The default gateway is usually an address that is automatically configured through DHCP. Typically, a default gateway will appear as 10.194.84.255 (although they usually end in .1 or .254 depending on the scope size) and serves as the point where a computer directs all its traffic to be further routed. As for IPv6, detailed instructions can be found in the post how-to-fix-ipv6-connectivity/, although it can also be verified 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 10.194.84.255 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:f5ea:6551:9502:e950%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): {93.125.104.79, 225.5.171.236}
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 c0:6b:a7:3b:00:fe
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 a7:cf:67:83:2e:75
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Actions to Take on Apple macOS / OSX
Regardless of whether you are running version 10.15.9, 11.3.4, or 12.0.6 of OSX/macOS, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Tools
One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of the information is only relevant at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, you can utilize sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose with a privacy warning, which should open Finder in the correct location. Just be mindful of the file sizes, which are typically around 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
