How To Fix MacOS Internet Connection
How the Functioning of Internet Addressing Takes Place
When accessing the Internet, you might have a Public IPv4 address such as 33.86.190.103 or an IPv6 address like 2000:360b:b05a:b439:5bdc:fe50:2dc6:3877. This can be verified at https://test-ipv6.com/. However, for those who are not technically inclined, communicating these addresses or even citing MAC addresses such as 59:62:f8:c3:56:ff can be prone to errors and become complex very quickly. Moreover, this does not provide any historical data, especially pertaining to past problems.
How to Reach Websites
In order to access a web page, such as https://torphy.name, the first step is to access a DNS server to translate the host portion (torphy) in combination with the Top Level Domain (name) of the URL to an IP address such as 189.41.203.114. When making web requests, your computer and browser actually send out their type, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured via DHCP. You are assigned a default gateway like 10.196.157.147 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer directs all its traffic to be routed onwards. For IPv6, a detailed explanation can be found in the post how-to-fix-ipv6-connectivity/, but you can verify this on Mac or Linux using the following commands:
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 10.196.157.147 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 fe80:71df:35aa:8de6:a1ad%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): {160.84.255.116, 196.219.168.6}
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 59:62:f8:c3:56: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 23:f9:3c:04:9f:c7
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you have the option of using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you are currently using, whether it’s 10.13.8, 11.1.1, or 12.3.6, there are a variety of troubleshooting tools available. However, these tools may not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams embracing remote work and the Work From Anywhere (WFA) concept.
Utilizing Pre-installed Scripts for Assistance
One of the tools available on OSX/macOS is the sudo wdutil info command, which provides a detailed output of current wireless settings in the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although many of these logs are only relevant at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs at /var/tmp/<blah>.tar.gz. For an interactive option (although minimal interaction is required), you can run sudo /usr/bin/sysdiagnose which will prompt a privacy warning. If not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to directly access the path. Keep in mind that the file sizes are around 300MB, more or less.
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