How Do You Test Mac IP Settings
Understanding Internet Addressing
When it comes to accessing the internet, you may be assigned a Public IPv4 address such as 150.71.27.185 or an IPv6 address like 2000:fa06:49d9:4043:15cf:336:9d8d:9279. These addresses can be verified at https://test-ipv6.com/. However, conveying these addresses to individuals who aren’t tech-savvy, or even mentioning MAC addresses like 05:95:ef:6d:e3:11, can be prone to errors and quickly become complicated. Moreover, this method does not provide any historical data, particularly when past issues arose.
Navigating the World Wide Web
When attempting to visit a web page such as https://little-daugherty.net, you start by accessing a DNS server to translate the combination of the host portion (little-daugherty) and the Top Level Domain (net) of the URL into an IP address like 211.112.39.217. Additionally, your computer and browser send their type with all web requests, 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
The default gateway is typically an automatically configured address via DHCP. It is likely that you will receive a default gateway such as 192.168.41.255 (although they usually end in .1 or .254 depending on the scope size), which is where your computer sends all its traffic to be routed onwards. As for IPv6, more in-depth information can be found in our guide how-to-fix-ipv6-connectivity/. However, on Mac or Linux systems, it can be verified with 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 192.168.41.255 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 fe80:7b71:761f:34da:3344%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): {44.223.177.27, 146.134.173.11}
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 05:95:ef:6d:e3:11
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 bf:90:62:cd:35:c2
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer to send the data to your router.
Solutions for Apple macOS / OSX Problems
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.5, 11.5.9, or 12.0.1, 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 essential, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Pre-Installed Scripts for Assistance
One incredibly useful tool on OSX/macOS is the sudo wdutil info, which provides the current wireless settings dump to the CLI. It can also 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 wireless settings at specific points in time, just like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, simply run sudo /usr/bin/sysdiagnose and it will issue a privacy warning. If it’s not run in the background, it should open Finder in the correct location, allowing you to navigate to /var/tmp, or you can use Finder with Cmd+Shift+G to point Finder to the path. Be mindful of the file sizes, which are approximately 300MB or more.
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