How To Check Mac IP Settings
The Functionality of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 5.142.86.234 or an IPv6 address like 2000:c5f0:5146:8f95:e113:5e10:439b:e. You can verify this at https://test-ipv6.com/. However, conveying these addresses to individuals who are not familiar with technology or discussing MAC addresses like b2:10:ef:00:58:de can be prone to errors and can become complex. Moreover, this method does not provide any historical information, especially back during past issues.
Navigating the Internet
To access a website like https://feeney-bogan.biz, you first contact a DNS server to convert the host segment (feeney-bogan) in combination with the Top Level Domain (biz) of the URL into an IP address like 93.93.123.253. Your computer and browser include its type 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
The Significance of Default Gateways
The default gateway is usually an automatically assigned address via DHCP. You receive a default gateway like 10.199.60.9 (although they generally end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed further. For IPv6, there is an in-depth examination on how-to-fix-ipv6-connectivity/ but you can verify on Mac or Linux 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 10.199.60.9 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 fe80:8ea6:ff3a:e53:e160%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): {146.227.132.110, 251.235.101.196}
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 b2:10:ef:00:58:de
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 5e:af:6f:08:90:40
}
Resolve Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Troubleshoot on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.13.4, 11.4.2, or 12.3.2, there are various tools available for resolving connectivity issues. 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).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info command, which displays the current wireless settings to the command line interface and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool provides a comprehensive range of logs, although much of it is only relevant to wireless connections, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose, but be cautious of the large file sizes of about 300MB. You can access the logs in Finder by navigating to the /var/tmp location or using Finder with Cmd+Shift+G to point to the path.
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