Support MacOS Internet
Functioning of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 or IPv6 address. The Public IPv4 address appears in the format of 156.204.174.21, while an IPv6 address may look like 2000:3333:535:189b:78c:2cde:e873:4871. The verification of this information can be done at https://test-ipv6.com/. However, conveying these addresses or MAC addresses like 72:e2:5d:6f:6e:a0 to those who may not be technologically inclined can become complicated and prone to errors. Additionally, it does not provide any historical data, which can be important when addressing previous issues.
Navigating the World Wide Web
When attempting to access a particular webpage such as https://crona.net, the process starts with communication with a DNS server. This server translates the host portion (crona) combined with the Top Level Domain (net) of the URL into an IP address, for example 86.232.102.222. It’s noteworthy that the computer and web browser reveal their type with all web requests. An example of the type of communication sent is: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Automated Gateways
Typically, the default gateway is automatically configured through DHCP. It typically appears in the form of an address like 10.1.53.23 (commonly ending in .1 or .254 based on the scope size). This default gateway is responsible for routing all of a computer’s traffic. For IPv6, a detailed explanation can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, the settings can be verified with the commands below:
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 10.1.53.23 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:f5f:a913:8bf7:3e55%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): {204.93.158.110, 154.150.247.61}
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 72:e2:5d:6f:6e:a0
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 7b:6a:96:f3:9a:14
}
Solutions for Wired and Wireless Connectivity Issues
Whether you are utilizing a wired or wireless (Wi-Fi) connection, you are operating at the physical and data layer to transmit data to your router.
Steps to Take on Apple macOS / OSX Systems
Irrespective of the version of OSX/macOS you are working on, be it 10.15.3, 11.0.7, or 12.1.5, there are various troubleshooting tools available. However, these tools do not provide a set of correlated values over time, which makes automated remote troubleshooting highly beneficial, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Commands for Troubleshooting
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be utilized to generate a wide range of logs, although much of it pertains to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose and it will display 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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