How Can I Check MacOS IP Settings
Understanding the Functioning of Internet Addressing
When using the Internet, you are allocated with a Public IPv4 address, for example, 235.247.215.192, or an IPv6 address such as 2000:e515:6484:fa48:4195:5f08:ff73:2928. You can verify this by visiting https://test-ipv6.com/. However, conveying these addresses to individuals who are not technologically savvy, or even identifying MAC addresses like 95:93:9e:2c:8b:42, can be prone to errors and can become complicated quickly. Moreover, this does not provide any historical data, particularly when past issues occurred.
Navigating the World Wide Web
In order to access a website such as https://goldner-powlowski.net, you first contact a DNS server to convert the host part (goldner-powlowski) along with the URL’s Top Level Domain (net), into an IP address like 232.208.123.180. Your computer and browser sends its type with every web request. For example, Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured through DHCP. You are assigned a default gateway such as 192.0.0.114 (although they usually end in .1 or .254 based on the scope size), and this is where your computer sends all its traffic to be routed further. For IPv6, you can find detailed information on how-to-fix-ipv6-connectivity/. On Mac or Linux, you can check with:
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 192.0.0.114 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:d44d:c136:23d7:877d%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): {92.190.138.227, 50.50.73.3}
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 95:93:9e:2c:8b:42
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 99:8f:cb:fc:a6:86
}
Resolving Issues with Wired and Wireless Connections
When it comes to transferring data to your router, it’s important to troubleshoot issues involving both wired and wireless (Wi-Fi) mediums at the physical and data layer.
Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS version 10.12.6, 11.4.2, or 12.3.7, there are various troubleshooting tools available. However, these tools may not provide a series of correlated values over time, especially for teams that rely on remote work and Work From Anywhere (WFA) setups.
Utilizing Pre-Installed Scripts
One convenient tool for OSX/macOS users is the sudo wdutil info command, which displays current wireless settings and can be configured to generate troubleshooting logs. Additionally, the more comprehensive sysdiagnose tool can be used to produce a wide range of logs related to wireless issues. Running it in the background with the command sudo nohup /usr/bin/sysdiagnose -u & will create logs in /var/tmp/<blah>.tar.gz, while running it interactively with sudo /usr/bin/sysdiagnose will provide a privacy warning and open Finder in the correct location or allow navigation to /var/tmp using Cmd+Shift+G. Keep in mind that the file sizes can be around 300MB.
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