How To Troubleshoot Apple IP Settings
Functions of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 183.187.6.186 or an IPv6 address like 2000:35e7:76ef:d17b:b10b:603b:68c5:cc6a. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not well-versed in technology, communicating these addresses or even referring to MAC addresses like 60:74:40:f3:58:a7 can quickly become complicated and prone to errors. Moreover, historical data is not accessible, especially regarding previous issues that occurred.
Navigating the World Wide Web
Accessing a web page, such as https://schuppe-renner.biz, involves the initial step of contacting a DNS server to translate the host portion (schuppe-renner) combined with the Top Level Domain (biz) of the URL into an IP address like 116.96.138.81. When making web requests, your computer and browser send their type, including:
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
Commonly, the default gateway is an address that is automatically configured via DHCP. You receive a default gateway like 192.168.153.247 (typically ending in .1 or .254 depending on the scope size), and this is where your computer directs all of its traffic to be routed onwards. To troubleshoot IPv6 connectivity on Mac or Linux, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/.
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 192.168.153.247 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:fcdc:8423:99b6:d2a4%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): {179.136.44.243, 10.115.101.147}
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 60:74:40:f3:58:a7
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 57:0c:c1:42:09:44
}
Resolving Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.15.7, 11.4.9, or 12.2.9, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. For this reason, automated remote troubleshooting becomes invaluable, especially for teams that have embraced remote work and the Work From Anywhere (WFA) model.
Useful Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose tool, which can generate a wide range of logs, although many of them are only related to wireless settings at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the following command:
sudo nohup /usr/bin/sysdiagnose -u &
For an interactive (although minimal interaction) experience, use the following command with a privacy warning:
sudo /usr/bin/sysdiagnose
When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are around 300MB.
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