How To Support Apple IP Settings
The Fundamentals of Internet Addressing
When connected to the Internet, you are assigned a Public IPv4 or IPv6 address. You can verify your address using https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, as well as MAC addresses, can be error-prone and complex, and it does not provide historical data.
Navigating the World Wide Web
When attempting to access a website such as https://cremin.org, your computer first contacts a DNS server to convert the URL into an IP address, such as 37.20.240.22. Your computer and browser also include type information in all web requests, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Understanding the Significance of Default Gateways
The default gateway is typically assigned automatically through DHCP and is the designated address for routing all traffic. For IPv6, you can refer to our guide how-to-fix-ipv6-connectivity/ or check on Mac or Linux using the 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 10.44.90.214 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 fe80:2d93:cf04:aaf3:b878%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): {4.28.125.170, 34.190.228.120}
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 78:69:4c:be:1c:ab
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 55:d3:38:ed:e6:cf
}
Troubleshooting and Resolving Connectivity Issues
Whether you are utilizing a wired or wireless (Wi-Fi) medium, the physical and data layer play a crucial role in transmitting data to your router.
Solutions for Apple macOS and OSX Users
Regardless of whether you are running OSX/macOS versions such as 10.15.8, 11.5.3, or 12.3.8, there are a variety of troubleshooting tools available. However, manual actions and scripts may not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have adopted remote work and Work From Anywhere (WFA) policies.
Pre-Installed Scripts for Troubleshooting
An extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool offers a more comprehensive solution, producing a wide range of logs (although many are only relevant to a specific point in time, similar to wdutil).
By running sudo nohup /usr/bin/sysdiagnose -u & in the background, logs will be written to /var/tmp/<blah>.tar.gz. For an interactive experience (albeit with minimal interaction), you can runsudo /usr/bin/sysdiagnose which will trigger a privacy warning. If 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 navigate to the specified path. It’s important to be mindful of the file sizes, which are typically around 300MB.
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