How To Understand Mac Internet Connection

Basics of Internet Addressing When using the Internet, you are assigned a unique Public IPv4 address, such as 41.226.104.206, or an IPv6 address, like 2000:a9ef:26e3:b03e:dfc8:db18:36a0:4bc1. Verifying this information can be done through https://test-ipv6.com/. However, for those who are not well-versed in technology, relaying or even identifying these addresses, as well as MAC addresses like 5f:24:45:cd:ea:cd, can be prone to errors and quickly become complex. Basics of Internet Addressing When using the Internet, you are assigned a unique Public IPv4 address, such as 41.226.104.206, or an IPv6 address, like 2000:a9ef:26e3:b03e:dfc8:db18:36a0:4bc1. Verifying this information can be done through https://test-ipv6.com/. However, for those who are not well-versed in technology, relaying or even identifying these addresses, as well as MAC addresses like 5f:24:45:cd:ea:cd, can be prone to errors and quickly become complex.

Basics of Internet Addressing

When using the Internet, you are assigned a unique Public IPv4 address, such as 41.226.104.206, or an IPv6 address, like 2000:a9ef:26e3:b03e:dfc8:db18:36a0:4bc1. Verifying this information can be done through https://test-ipv6.com/. However, for those who are not well-versed in technology, relaying or even identifying these addresses, as well as MAC addresses like 5f:24:45:cd:ea:cd, can be prone to errors and quickly become complex. Furthermore, this process does not provide any historical data, especially regarding past issues.

When attempting to reach a webpage, such as https://donnelly.com, the first step is to access a DNS server to translate the host portion (donnelly) in conjunction with the Top Level Domain (com) of the URL to an IP address, such as 76.110.255.10. Every web request sent from your computer and browser actually contains its type, such as
Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.

Understanding the Significance of Default Gateways

In most cases, your default gateway is automatically configured through DHCP and is assigned an address, like 172.21.71.59 (typically ending in .1 or .254 depending on the scope size). This is the location where your computer routes all of its traffic. A deeper exploration of IPv6 connectivity is available at how-to-fix-ipv6-connectivity/, or alternatively, you can verify this on Mac or Linux with the following command:

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  172.21.71.59    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:ea0a:bf58:893:1bdf%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): {226.12.135.111, 65.52.8.98}
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 5f:24:45:cd:ea:cd
  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 b9:b6:c6:5b:95:fe
}

Addressing Wired and Wireless Connectivity Issues

When it comes to sending data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.

Solutions for Apple macOS / OSX Users

Regardless of whether you are working with OSX/macOS versions such as 10.12.9, 11.4.1, or 12.3.6, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time, which is where automated remote troubleshooting becomes valuable, especially for remote work and Work From Anywhere (WFA) teams.

Effective Built-in Scripts for Troubleshooting

A 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 troubleshooting logs. Additionally, the sysdiagnose tool offers a comprehensive range of logs, although much of it is only point-in-time in relation to wireless, similar to wdutil.

To run the sysdiagnose tool in the background and generate logs, the command sudo nohup /usr/bin/sysdiagnose -u & can be used. Alternatively, for interactive use, the command sudo /usr/bin/sysdiagnose will provide a privacy warning and open Finder in the correct location, or users can navigate to /var/tmp using Finder with Cmd+Shift+G. It’s important to note that the file sizes are approximately 300MB.

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