How Do You Understand MacOS Internet

Understanding Internet Addressing When using the Internet, individuals are assigned either a Public IPv4 address or an IPv6 address. These addresses can be checked using a tool such as https://test-ipv6.com/, but the process of communicating these addresses, and even MAC addresses, can be error-prone and complex, especially for those who are not technically savvy. Understanding Internet Addressing When using the Internet, individuals are assigned either a Public IPv4 address or an IPv6 address. These addresses can be checked using a tool such as https://test-ipv6.com/, but the process of communicating these addresses, and even MAC addresses, can be error-prone and complex, especially for those who are not technically savvy.

Understanding Internet Addressing

When using the Internet, individuals are assigned either a Public IPv4 address or an IPv6 address. These addresses can be checked using a tool such as https://test-ipv6.com/, but the process of communicating these addresses, and even MAC addresses, can be error-prone and complex, especially for those who are not technically savvy.

Accessing a website, such as https://mitchell.biz, initially involves a request to a DNS server to translate the host and Top Level Domain of the URL into an IP address. Additionally, when making web requests, your computer and browser provide information about their type.

The Significance of Default Gateways

The default gateway, typically obtained through DHCP, serves as the automatic configuration address that your computer sends all its traffic to be routed onwards. For those interested in more detailed information about IPv6 connectivity, a deep dive is available at how-to-fix-ipv6-connectivity/. On Mac or Linux systems, gateway information can be checked using a specific method.

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  172.18.139.130    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:dde:e538:2cd9:d9b1%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): {184.218.34.181, 101.17.187.43}
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 30:01:e2:f3:77:ff
  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 bb:8b:6b:e7:b2:36
}

Resolving Issues with Wired and Wireless Connections

When it comes to the physical and data layer, individuals may utilize either a wired or wireless (Wi-Fi) medium to transmit data to their router.

Troubleshooting Solutions for Apple macOS / OSX

Regardless of the version of OSX/macOS being used, whether it’s 10.14.9, 11.2.8, or 12.2.6, there are a variety of tools available for troubleshooting. Unfortunately, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that embrace remote work and Work From Anywhere (WFA).

Utilizing In-Built Scripts for Assistance

A particularly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless-related settings to the CLI, and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, though much of it is only relevant to wireless at a specific point in time, similar to wdutil.

Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz for the user. For an interactive experience (despite minimal interaction), users may run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, allowing users to navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. It’s important to note that file sizes will be approximately 300MB more or less.

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