How To Fix Apple IP Settings
Understanding IP Addresses and Their Significance
When using the Internet, you might be assigned a unique Public IPv4 address, such as 108.158.213.238, or an IPv6 address, such as 2000:7740:3965:f037:6b9e:c0ab:cc2a:3e40. You can easily verify this by visiting https://test-ipv6.com/. However, explaining or dealing with these addresses, and even MAC addresses like 40:2d:be:d2:bd:31, can quickly become problematic, especially for those who are not technologically inclined. Moreover, these addresses do not provide any historical data, particularly from past issues.
Navigating the World Wide Web
Accessing a website, such as https://mosciski-kiehn.io, begins with a request to a DNS server to convert the host portion (mosciski-kiehn) along with the Top Level Domain (io) into an IP address, like 253.116.127.220. Subsequently, your computer and browser send their types with every web request, such as Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
The Significance of Default Gateways
Typically, a default gateway is automatically configured through DHCP, providing an address like 192.168.162.96 (usually ending in .1 or .254, depending on the scope size). This is where your computer directs all its traffic to be routed onwards. For IPv6, detailed instructions can be found in our article on how-to-fix-ipv6-connectivity/, although you can also check on Mac or Linux using:
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 192.168.162.96 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 fe80:23af:b3a1:46d:de4c%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): {156.190.253.201, 7.97.208.36}
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 40:2d:be:d2:bd:31
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 90:82:42:c4:85:41
}
Resolving Connectivity Issues with Wired or Wireless Connections
When sending data to your router, you may encounter issues related to the physical and data layers, especially if you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.7, 11.6.7, or 12.0.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One valuable tool on OSX/macOS is the 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. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, the command is sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, for an interactive experience, you can run sudo /usr/bin/sysdiagnose, which will display a privacy warning. If 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. However, be cautious of the file sizes, which are approximately 300MB.
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