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Understanding Internet Addressing Mechanism When using the Internet, individuals may be assigned a Public IPv4 address such as 168.70.89.168 or an IPv6 address such as 2000:d7e9:3d4:4f6a:5d9e:eceb:444a:c1ab. Users can verify this information by visiting https://test-ipv6.com/. However, explaining or communicating these addresses, and even mentioning MAC addresses like 1e:3b:0e:af:20:b3, can be cumbersome and prone to errors. Understanding Internet Addressing Mechanism When using the Internet, individuals may be assigned a Public IPv4 address such as 168.70.89.168 or an IPv6 address such as 2000:d7e9:3d4:4f6a:5d9e:eceb:444a:c1ab. Users can verify this information by visiting https://test-ipv6.com/. However, explaining or communicating these addresses, and even mentioning MAC addresses like 1e:3b:0e:af:20:b3, can be cumbersome and prone to errors.

Understanding Internet Addressing Mechanism

When using the Internet, individuals may be assigned a Public IPv4 address such as 168.70.89.168 or an IPv6 address such as 2000:d7e9:3d4:4f6a:5d9e:eceb:444a:c1ab. Users can verify this information by visiting https://test-ipv6.com/. However, explaining or communicating these addresses, and even mentioning MAC addresses like 1e:3b:0e:af:20:b3, can be cumbersome and prone to errors. Moreover, it does not provide historical data, particularly regarding past issues.

Accessing a website, such as https://schmitt.io, involves an initial connection to a DNS server in order to translate the host section (schmitt) and the Top Level Domain (io) of the URL into an IP address, like 137.24.110.167. When making web requests, your computer and browser also transmit their type, such as:
Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16

Significance of Default Gateways

The default gateway is typically an automatically assigned address through DHCP. It is usually a default gateway like 192.0.0.140 (though it often ends in .1 or .254 based on the scope size), and it serves as the router for all outgoing traffic from your computer. For IPv6, detailed instructions can be found in our article how-to-fix-ipv6-connectivity/. Alternatively, on Mac or Linux systems, you can perform the check by using 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  192.0.0.140    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:bfc8:5b89:d3f8:3732%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): {11.42.231.19, 149.197.103.217}
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 1e:3b:0e:af:20:b3
  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 a3:f7:0d:85:90:ae
}

Resolving Issues with Wired and Wireless Connections

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

Steps for Troubleshooting on Apple macOS / OSX

No matter which version of OSX/macOS you are currently using, whether it’s 10.13.4, 11.2.7, or 12.1.3, 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 valuable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) concept.

Utilizing In-Built Scripts

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

Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. For interactive use, you can run sudo /usr/bin/sysdiagnose, which will give a privacy warning and open Finder in the correct location. Alternatively, you can navigate to the /var/tmp directory or use Finder with Cmd+Shift+G to navigate to the path. Keep in mind that the file sizes are approximately 300MB.

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