How Do You Understand Mac Issues

The Basics of Internet Addressing When using the Internet, you will be assigned a Public IPv4 address such as 50.113.123.74 or an IPv6 address like 2000:ee47:ff11:3206:511a:a0c7:29cd:3954. You can verify this at https://test-ipv6.com/. However, explaining or communicating these addresses, as well as MAC addresses like 2f:b6:fe:7d:1d:1f, can be prone to errors and become complex. The Basics of Internet Addressing When using the Internet, you will be assigned a Public IPv4 address such as 50.113.123.74 or an IPv6 address like 2000:ee47:ff11:3206:511a:a0c7:29cd:3954. You can verify this at https://test-ipv6.com/. However, explaining or communicating these addresses, as well as MAC addresses like 2f:b6:fe:7d:1d:1f, can be prone to errors and become complex.

The Basics of Internet Addressing

When using the Internet, you will be assigned a Public IPv4 address such as 50.113.123.74 or an IPv6 address like 2000:ee47:ff11:3206:511a:a0c7:29cd:3954. You can verify this at https://test-ipv6.com/. However, explaining or communicating these addresses, as well as MAC addresses like 2f:b6:fe:7d:1d:1f, can be prone to errors and become complex. Moreover, it lacks historical data, especially for previous issues.

In order to reach a website such as https://denesik.biz, you first need to access a DNS server to convert the host portion (denesik) combined with the Top Level Domain (biz) of the URL to an IP address like 3.64.169.135. Whenever your computer and browser make web requests, they actually include their type, for example:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A

Understanding the Significance of Default Gateways

Typically configured automatically through DHCP, your default gateway is an essential part of your network. It usually appears in the form of an address like 172.26.63.7 (often ending in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed further. For a more in-depth look at IPv6, you can refer to our detailed guide on how-to-fix-ipv6-connectivity/, or check on Mac or Linux with:

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  172.26.63.7    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   fe80:46de:3ae8:762f:9049%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): {97.241.56.137, 155.21.99.5}
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 2f:b6:fe:7d:1d:1f
  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 e1:77:b4:e8:8a:30
}

Fixing Issues with Wired and Wireless Connections

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

Troubleshooting Strategies for Apple macOS / OSX

Regardless of whether you are running OSX/macOS version 10.13.5, 11.3.6, or 12.2.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).

Useful Built-in Scripts

An incredibly useful tool for OSX/macOS is sudo wdutil info, which provides a dump of the current wireless-related settings in the CLI and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are point-in-time related to wireless, similar to wdutil.

To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose and be aware of the large file sizes, typically around 300MB.

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