How Do You Fix Apple IP Settings
The Functionality of IP Addressing
When connecting to the Internet, you are assigned a unique Public IPv4 address, such as 41.242.188.123, or an IPv6 address, such as 2000:2c9c:4c8f:a27b:781:b55c:7b07:e813. You can verify this information using https://test-ipv6.com/. However, the task of conveying these addresses to non-technical users, or referencing MAC addresses like 7e:81:62:1f:09:c1, can be prone to error and become complex. In addition, this method lacks historical data, especially for previous issues.
Navigating the Internet
When attempting to access a website, for example, https://pagac-von.biz, you first contact a DNS server to translate the host portion (pagac-von) in combination with the URL’s Top Level Domain (biz) into an IP address, such as 237.63.147.229. Your computer and browser send their type with all web requests, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
The Significance of Default Gateways
By default, your gateway is an address configured automatically via DHCP, such as 10.131.121.2 (although they typically end in .1 or .254 depending on the scope size), and serves as the destination for all traffic that your computer forwards. For IPv6, there is an in-depth guide 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 10.131.121.2 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 fe80:3f77:f2e4:4606:a4e%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): {102.132.109.73, 148.230.57.141}
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 7e:81:62:1f:09:c1
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 b2:0c:36:bc:3f:d9
}
Solve Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Effective Troubleshooting for Apple macOS / OSX
Regardless of whether you are running OSX/macOS 10.13.9, 11.6.6, or 12.0.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Leveraging Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless related settings to the CLI. This tool 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 only relevant to wireless networks, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz. For an interactive run, you can use sudo /usr/bin/sysdiagnose, which 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 or use Finder with Cmd+Shift+G to point Finder to the path. Be mindful of the file sizes, which are around 300MB more or less.
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