How Can I Understand Apple IP Settings
Understanding Internet Protocol Addressing
When connecting to the Internet, you will be assigned a Public IPv4 address such as 238.139.91.117 or an IPv6 address such as 2000:96a0:60ce:6eb6:8aad:89e3:c696:3a7e. These addresses can be verified at https://test-ipv6.com/. However, conveying these addresses, along with MAC addresses like d0:93:6b:42:a9:4b, to individuals who are not technologically savvy can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, particularly regarding past issues.
Navigating the World Wide Web
When attempting to visit a website, such as https://greenholt.org, your first step is to access a DNS server to convert the combination of the host portion (greenholt) and the Top Level Domain (org) of the URL into an IP address like 96.11.180.213. Your computer and browser also include information about its type in all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP. Typically, a default gateway like 192.0.0.10 is used (though they usually end in .1 or .254 depending on the scope size), and this is the destination to which your computer sends all of its traffic to be forwarded. More information about IPv6 can be found in our in-depth guide on how-to-fix-ipv6-connectivity/ or can be checked on Mac or Linux using the following command:
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 192.0.0.10 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 fe80:9652:c7ca:b562:879d%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): {244.73.154.205, 47.141.186.23}
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 d0:93:6b:42:a9:4b
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 73:58:68:3f:4a:7e
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Strategies for Apple macOS / OSX Users
No matter which version of OSX/macOS you are currently using - be it 10.12.3, 11.6.7, or 12.0.6 - 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 embrace remote work and Work From Anywhere (WFA).
Utilize the System’s Built-in Scripts
A useful tool for troubleshooting on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs. Furthermore, the sysdiagnose tool can be utilized to generate a wide range of logs related to wireless, albeit many are point-in-time only, similar to wdutil.
Running the command sudo nohup /usr/bin/sysdiagnose -u & will execute the sysdiagnose tool in the background, writing logs to /var/tmp/<blah>.tar.gz. Alternatively, you can run the command interactively using 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. Be mindful of the file sizes, which can be around 300MB more or less.
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