How Do You Understand Apple IP Settings
Functionality of Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address such as 158.143.135.4 or an IPv6 address like 2000:c3c3:26ba:e228:a748:eac7:65f0:d6f0. These details can be verified at https://test-ipv6.com/. However, conveying these addresses, or even referencing MAC addresses like e0:a1:48:19:6c:00, can be complex and susceptible to errors, especially for those without technical expertise. Furthermore, this method does not provide any historical data, which is particularly problematic in resolving past issues.
Procedure to Reach the World Wide Web
When attempting to access a web page such as https://oconner.com, the first step involves contacting a DNS server to convert the host portion (oconner) combined with the Top Level Domain (com) of the URL into an IP address like 151.128.253.46. Every web request from your computer and browser also includes its type, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
The default gateway is typically an automatically configured address obtained through DHCP. It usually ends in .1 or .254 based on the scope size, and could be something like 172.30.131.93. This is the location where your computer directs all its traffic to be routed further. For IPv6, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/, but you can verify it 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 172.30.131.93 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:ca61:6c12:8736:10ac%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): {205.47.9.145, 204.74.86.163}
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 e0:a1:48:19:6c:00
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 e0:aa:20:77:f7:77
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using either a wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Apple macOS / OSX Troubleshooting Guide
Regardless of the version of OSX/macOS you have, whether it’s 10.13.1, 11.1.9, or 12.2.8, there are various troubleshooting tools available. However, the manual actions and scripts don’t provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that practice remote work and Work From Anywhere (WFA).
Useful Built-in Scripts for macOS Troubleshooting
A valuable 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 generate specific logs for troubleshooting. Additionally, the more comprehensive sysdiagnose tool can be utilized to generate a wide range of logs (although much of it is only relevant to wireless settings, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will produce logs in /var/tmp/<blah>.tar.gz. Alternatively, you can run sudo /usr/bin/sysdiagnose interactively, 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 Cmd+Shift+G in Finder. Keep in mind that the file sizes can be around 300MB or so.
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