How Do You DiagnOSe Apple IP Settings
Understanding the Functioning of Internet Addressing
When using the Internet, individuals may come across different types of IP addresses such as Public IPv4 address and IPv6 addresses. These can be verified through websites like https://test-ipv6.com/. However, for those who are not technically inclined, conveying or handling these addresses can be challenging and prone to errors, especially when referencing MAC addresses like 14:07:13:ac:2c:75. Moreover, there is a lack of historical data, particularly concerning past issues.
Navigating the World Wide Web
In order to access a web page, such as https://pouros-boyer.name, one must first access a DNS server to convert the URL’s host portion (pouros-boyer) along with the Top Level Domain (name) into an IP address, such as 126.137.143.200. It is interesting to note that a computer and its browser include its type in all web requests, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
By default, the gateway address is automatically configured through DHCP. The default gateway, such as 192.0.0.56 (which typically ends in .1 or .254 depending on the scope size), is where a computer dispatches all its traffic to be further routed. For IPv6, users can learn more from the detailed article how-to-fix-ipv6-connectivity/, and for Mac or Linux users, they can verify 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 192.0.0.56 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 fe80:5f66:cdbb:68b7:9b60%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): {200.103.82.84, 16.140.199.132}
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 14:07:13:ac:2c:75
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 0d:66:a0:7d:fd:5c
}
Resolving Connectivity Issues with Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions like 10.11.6, 11.3.5, or 12.0.2, there are a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, making it challenging to assess the situation. This is where automated remote troubleshooting becomes invaluable, especially for teams practicing remote work and Work From Anywhere (WFA).
Utilizing In-Built Scripts for Assistance
One of the useful tools on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the command line interface (CLI) and 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 many of them are point-in-time data in relation to wireless, similar to wdutil.
Running the command sudo nohup /usr/bin/sysdiagnose -u & will execute the sysdiagnose tool in the background, writing logs to /var/tmp/<blah>.tar.gz. For an interactive mode, the command sudo /usr/bin/sysdiagnose can be used, which will display a privacy warning. When not run in the background, it should open Finder in the correct location, or users can navigate to /var/tmp using Finder with Cmd+Shift+G. However, it’s important to note that the file sizes can be around 300MB or more.
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