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. 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.

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.

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

Video Title Channel
Securing macOS Big Sur Hands-On Mac
Mac Activity Monitor - How to Troubleshoot Your Mac Hands-On Mac
macOS Big Sur - What's New in Apple macOS 11 Hands-On Mac
Spotlight on Spotlight - Hands-On Mac 7 Hands-On Mac
On the Road to Big Sur 2 - Compatibility Hands-On Mac
Table 1.0 - Video Help



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