Understand Apple Internet
The Functionality of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address such as 159.123.181.173 or an IPv6 address like 2000:678e:8f4f:8e5d:dd72:680f:93e0:c298. This can be verified at https://test-ipv6.com/. However, for those not well-versed in technology, attempting to communicate these addresses, or even reciting MAC addresses like 5e:5b:cd:cc:6e:8e, can lead to errors and complications. Moreover, this method does not provide any historical data, particularly when past issues have arisen.
Navigating the Internet
When attempting to access a website such as https://strosin.net, the first step involves contacting a DNS server to convert the host section (strosin) in combination with the Top Level Domain (net) of the URL into an IP address, for example, 72.238.123.167. With every web request, your computer and browser actually transmit its type, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
Typically, your default gateway is an automatically configured address obtained via DHCP. A default gateway like 192.168.74.229 (often ending in .1 or .254, based on the scope size) is where your computer directs all its traffic to be routed onwards. For IPv6, we have a comprehensive guide on how-to-fix-ipv6-connectivity/, although you can verify this 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 192.168.74.229 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:bf52:3620:d0d0:37c0%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): {177.90.46.211, 159.155.148.227}
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 5e:5b:cd:cc:6e:8e
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 ab:9c:49:23:c7:de
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of whether you are running 10.15.8, 11.5.6, or 12.1.8, there are various troubleshooting tools available for Apple macOS / OSX. However, these manual actions and scripts do not provide a series of correlated values over time. Automated remote troubleshooting becomes essential, especially for teams that practice remote work and Work From Anywhere (WFA).
Effective Built-in Tools for Troubleshooting
A very useful tool for troubleshooting on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, though much of it is point-in-time only in relation to wireless, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you want to run it interactively, use the command sudo /usr/bin/sysdiagnose and it will give a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to the /var/tmp folder using Finder with Cmd+Shift+G. Keep in mind that the file sizes are about 300MB, more or less.
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