How Can I Test MacOS IP Settings
Understanding the Functioning of Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address such as 199.7.236.122 or an IPv6 address like 2000:38f2:9a38:c1f3:920e:1b96:b796:d898. You can verify this information from https://test-ipv6.com/. However, for individuals with limited technical knowledge, conveying these addresses or identifying MAC addresses like 11:3f:77:06:a4:0f can be prone to errors and quickly become complex. Furthermore, this does not provide any historical data, especially from previous occurrences of problems.
Navigating Websites
In order to access a website such as https://kautzer.io, you first contact a DNS server to convert the host portion (kautzer) along with the Top Level Domain (io) of the URL into an IP address like 151.76.156.41. Additionally, your computer and browser transmit its type with every web request, for example:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. As a result, you receive a default gateway like 172.25.4.242 (although they usually end in .1 or .254 depending on the scope size), which serves as the point where your computer routes all traffic for further transmission. For a comprehensive guide on IPv6, you can refer to how-to-fix-ipv6-connectivity/ or use the following command for verification on Mac or Linux:
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 172.25.4.242 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:cdda:ee6a:3439:e43b%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): {216.50.144.137, 134.125.254.158}
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 11:3f:77:06:a4:0f
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 f6:91:97:c5:6b:57
}
Fixing Connectivity Issues for Wired and Wireless Networks
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.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you’re using - whether it’s 10.14.8, 11.6.2, or 12.2.1 - there are numerous troubleshooting tools available. 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).
Useful Built-in Scripts
A very helpful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and 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 point in time only in relation to wireless, similar to the wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you want to run it interactively (although there is not much interaction), you can run sudo /usr/bin/sysdiagnose and it will give a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp manually. Keep in mind that the file sizes are about 300MB more or less.
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P.S. Tips For Remote Network and Client Support
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