How Do You Understand Mac Internet Connection
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 57.128.8.123 or an IPv6 address like 2000:2680:acda:ffa9:94ea:bde6:575f:7610. You can verify this allocation at https://test-ipv6.com/. Communicating these addresses, and even MAC addresses like 9f:66:e1:df:39:94, can be challenging for non-technical individuals. Furthermore, this method does not provide any historical data, particularly in relation to past issues.
Navigating the World Wide Web
Accessing a website, such as https://greenholt.com, involves initially contacting a DNS server to convert the host portion (greenholt) in combination with the Top Level Domain (com) of the URL into an IP address, such as 230.124.113.5. Every web request from your computer and browser is accompanied by its specific 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
By default, your gateway is an address that is automatically configured through DHCP. Typically, you will receive a default gateway like 192.0.0.162 (although they usually end in .1 or .254 based on the scope size), and this is where your computer forwards all of its traffic to be routed further. For further guidance on IPv6, an in-depth explanation can be found at how-to-fix-ipv6-connectivity/, or you can check on Mac or Linux using:
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 192.0.0.162 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:f354:b84f:3d01:9972%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): {107.242.233.61, 150.49.45.173}
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 9f:66:e1:df:39:94
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 aa:c6:3d:a0:32:8c
}
Resolve Issues with Wired or Wireless Connectivity
When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Options for Apple macOS / OSX
Regardless of the version of OSX/macOS, whether it’s 10.12.5, 11.5.8, or 12.3.3, there are various tools available for troubleshooting. 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 adopt remote work and Work From Anywhere (WFA) policies.
Useful Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Moreover, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, even though much of it is only point-in-time data related to wireless, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz, or to run it interactively with sudo /usr/bin/sysdiagnose, keep in mind the file size of about 300MB or more.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
