How To Check MacOS IP Settings
Understanding Internet Address Allocation
When connecting to the internet, you will receive a public IPv4 address, such as 6.80.35.253, or an IPv6 address, like 2000:3958:e990:32f3:4d3e:4749:b492:72e1. You can verify this information by visiting https://test-ipv6.com/. However, relaying these addresses, and even MAC addresses, such as 70:7f:e5:a9:a1:54, in a non-technical manner can lead to errors and complex communication. Moreover, this approach does not provide historical data, particularly regarding previous issues.
Navigating the World Wide Web
Accessing a website, such as https://beer.com, involves an initial interaction with a DNS server to translate the host portion (beer) and the Top Level Domain (com) of the URL into an IP address, like 24.143.31.234. Notably, your computer and browser send their specifications with each web request, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
In most cases, your default gateway is automatically configured via DHCP and is assigned an address, such as 172.27.139.74 (usually ending in .1 or .254 based on the scope size). This is the point to which your computer directs all its traffic for further routing. For an in-depth guide on IPv6 connectivity troubleshooting, refer to how-to-fix-ipv6-connectivity/, or perform checks on Mac or Linux using:
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 172.27.139.74 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 fe80:76f:ea77:aaae:70f3%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): {161.223.190.166, 117.73.161.66}
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 70:7f:e5:a9:a1:54
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 79:99:6c:95:f9:04
}
Troubleshooting Connectivity Issues
When dealing with data transmission at the physical and data layer, it’s important to consider whether you are using a wired or wireless (Wi-Fi) medium to send the data to your router.
Tips for Addressing Connectivity Problems on Apple Devices
Regardless of whether you are using OSX or macOS version 10.11.8, 11.1.6, or 12.2.6, there are various resources available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that support remote work and Work From Anywhere (WFA).
Leveraging Built-in Tools for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings, and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to a point in time in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command:
sudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience, run sudo /usr/bin/sysdiagnose but keep in mind the large file size of about 300MB. After running the command, Finder will open in the correct location, or you can navigate to /var/tmp. Just be mindful of the file sizes, which can range around 300MB.
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