How Do You Understand OSX Internet

Understanding Internet Addressing When using the Internet, you are assigned a Public IPv4 or IPv6 address, such as 110.254.190.237 or 2000:4db9:302:e972:d20d:b978:c35f:36db. You can verify this through https://test-ipv6.com/. However, explaining these addresses to individuals who are not technologically savvy can be prone to errors and quickly become complex. Understanding Internet Addressing When using the Internet, you are assigned a Public IPv4 or IPv6 address, such as 110.254.190.237 or 2000:4db9:302:e972:d20d:b978:c35f:36db. You can verify this through https://test-ipv6.com/. However, explaining these addresses to individuals who are not technologically savvy can be prone to errors and quickly become complex.

Understanding Internet Addressing

When using the Internet, you are assigned a Public IPv4 or IPv6 address, such as 110.254.190.237 or 2000:4db9:302:e972:d20d:b978:c35f:36db. You can verify this through https://test-ipv6.com/. However, explaining these addresses to individuals who are not technologically savvy can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, especially during past issues.

In order to access a website like https://kutch.net, your computer first contacts a DNS server to translate the host (kutch) and the Top Level Domain (net) of the URL into an IP address, such as 98.253.253.154. Additionally, your computer and browser communicates its specifications with each web request, for example:
Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285

The Significance of Default Gateways

The default gateway is typically an address that is configured automatically via DHCP. This default gateway, such as 172.31.53.235 (often ending in .1 or .254 depending on the scope size), is where your computer directs all of its traffic to be routed onwards. For IPv6, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/ or check on Mac or Linux 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  172.31.53.235    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   fe80:77d4:e045:f187:c704%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): {84.147.234.32, 107.1.85.41}
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 47:20:f1:d6:76:2a
  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 a9:2f:e0:4a:f2:61
}

Resolve 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 Tips for Apple macOS / OSX

Regardless of the version of OSX/macOS you are using, whether it’s 10.11.4, 11.0.4, or 12.3.8, there are various tools available for resolving issues. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly useful, especially for teams that adopt remote work and Work From Anywhere (WFA) policies.

Utilizing Built-in Scripts to Aid Troubleshooting

An extremely useful tool on OSX/macOS is 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. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only point-in-time information in relation to wireless, similar to wdutil.

To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (despite the minimal interaction), you can use the command sudo /usr/bin/sysdiagnose, but be prepared for file sizes of around 300MB.

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