How Can I Understand OSX Internet
Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 222.82.192.10, or an IPv6 address, like 2000:32af:72de:9e4c:1638:a3b9:8101:d6b0. You can verify this by visiting https://test-ipv6.com/. However, for individuals who are not very tech-savvy, communicating these addresses or even referencing MAC addresses, such as 36:34:9e:01:e0:39, can be prone to errors and become complicated very quickly. Furthermore, this does not provide any historical data, especially with regards to previous issues.
Navigating the Internet
In order to access a website, such as https://keebler-kessler.com, you first connect to a DNS server to translate the host portion (keebler-kessler) along with the Top Level Domain (com) of the URL into an IP address, such as 88.132.27.66. Your computer and browser automatically include its type in all web requests, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
Your default gateway is typically an address that is automatically configured via DHCP. A default gateway, such as 172.25.139.43 (although they usually end in .1 or .254 depending on the scope size), is where your computer sends all of its traffic to be routed onwards. For IPv6, there is an in-depth guide on how-to-fix-ipv6-connectivity/ but you can also check 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 172.25.139.43 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 fe80:95ba:1675:106b:4ac6%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): {121.162.89.255, 241.135.183.80}
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 36:34:9e:01:e0:39
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 40:e7:30:03:b0:b6
}
Ways to Resolve Connectivity Issues with Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.11.3, 11.0.5, or 12.2.1, there is a variety of troubleshooting tools available. However, these manual interventions and scripts do not provide a series of interconnected values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One tool that is particularly useful on 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 troubleshooting logs. Furthermore, for a more comprehensive range of logs related to wireless networks, the sysdiagnose tool can be utilized (although much of it is only relevant at a specific point in time, similar to wdutil).
To run the sysdiagnose tool in the background and generate 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, you can use the command sudo /usr/bin/sysdiagnose, although it will prompt a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. Keep in mind that the file sizes are approximately 300MB.
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 🏠🏝🛰.
