How Do You Fix Mac Internet Connection

The Fundamentals of Internet Addressing

When you’re on the Internet, you are assigned a Public IPv4 address, like 116.48.91.147, or an IPv6 address, such as 2000:e5cb:811d:9e63:53f5:e1cb:d397:9789. You can verify this at https://test-ipv6.com/. However, explaining or communicating these addresses to individuals who are not technically inclined, or even mentioning MAC addresses like 3f:38:1b:7f:50:f8, can lead to errors and complexity. Moreover, this information does not provide any historical data, particularly when past issues occurred.

Navigating the World Wide Web

When you want to visit a website, such as https://koch.com, your initial step is to contact a DNS server to convert the host part (koch) combined with the Top Level Domain (com) of the URL to an IP address, like 205.205.86.174. Your computer and browser automatically transmit this information with all web requests, for example:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko

Understanding the Significance of Default Gateways

Usually, your default gateway is an automatically configured address through DHCP. You receive a default gateway like 192.168.98.40 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic for further routing. For IPv6, detailed instructions can be found in how-to-fix-ipv6-connectivity/, or you can verify 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  192.168.98.40    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   fe80:5ec3:ca94:d52f:4076%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): {54.32.164.212, 255.55.62.254}
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 3f:38:1b:7f:50:f8
  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 ed:f5:52:94:c1:bd
}

Resolve Issues with Wired and Wireless Connections

When it comes to sending data to your router, you might 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 have, whether it’s 10.12.2, 11.5.6, or 12.0.7, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).

Helpful Scripts Integrated in macOS / OSX

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

To run sysdiagnose in the background and write logs to “/var/tmp/.tar.gz,” use the command “sudo nohup /usr/bin/sysdiagnose -u &.” If you prefer to run it interactively, you can use “sudo /usr/bin/sysdiagnose,” which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to “/var/tmp” using Finder with Cmd+Shift+G or through the path. Keep in mind that the file sizes are approximately 300MB.

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Table 1.0 - Video Help