How Can I Understand Apple Internet Connection
Understanding IP Addressing
When using the Internet, you may receive a Public IPv4 address such as 202.195.166.162 or an IPv6 address like 2000:17f9:9545:e18b:c05e:9bee:e09a:4f33. One way to verify this information is by visiting https://test-ipv6.com/. Communicating these addresses, or even referencing MAC addresses like 30:d2:57:ad:a6:22, can be a challenging task for those who are not technologically inclined. Moreover, it does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
In order to access a web page, such as https://hirthe.com, your initial step involves reaching out to a DNS server to translate the host portion (hirthe) combined with the Top Level Domain (com) of the URL into an IP address, for example 187.148.235.28. When making web requests, your computer and browser include information about its type, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is typically an address that is automatically configured via DHCP. For instance, you might be assigned a default gateway like 172.25.57.237, with common endings being .1 or .254 based on the scope size. This is where your computer channels all its traffic to be routed onwards. For those interested in learning more about IPv6, a detailed guide can be found at how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux, you can run a check using the following method:
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 172.25.57.237 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:d618:f893:5cae:e1af%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): {80.224.97.59, 85.99.235.169}
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 30:d2:57:ad:a6:22
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 9d:2d:c1:3e:16:88
}
Fixing Issues with Wired and Wireless Connections
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.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of whether you are using OS X/macOS version 10.11.9, 11.1.7, 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 particularly useful, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Useful Built-in Scripts
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless related settings and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only point-in-time information related to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. Alternatively, for an interactive run (although there is not much interaction), you can execute sudo /usr/bin/sysdiagnose and it will give a privacy warning. When not run in the background, it should open Finder in the correct location, allowing you to navigate to /var/tmp, or use Finder with Cmd+Shift+G to locate the path. However, be mindful of the file sizes, which are approximately 300MB.
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