Test OSX IP Settings
An Explanation of Internet Addressing
When using the Internet, individuals often receive either a Public IPv4 address, such as 147.1.35.246, or an IPv6 address like 2000:93a2:2043:4023:f138:b8cf:f81d:41e2. This information can be verified at https://test-ipv6.com/. Communicating and transcribing these addresses, as well as MAC addresses (e.g. 4b:0c:0f:18:93:83) may be prone to errors and become complex for individuals not well-versed in technology. Furthermore, this method does not provide any historical data, particularly when addressing previous issues.
Navigating the World Wide Web
To access a website such as https://wiza.info, the first step is to connect to a DNS server in order to translate the host portion (wiza) and the Top Level Domain (info) of the URL into an IP address, like 212.190.125.179. Whenever the computer and browser make a web request, they typically transmit their type, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Understanding the Significance of Default Gateways
The default gateway is generally an address that is automatically configured via DHCP. Individuals obtain a default gateway, such as 172.25.165.208 (although it typically ends in .1 or .254 based on the scope size), and this is where the computer forwards all of its traffic for routing. For a detailed explanation of IPv6, refer to how-to-fix-ipv6-connectivity/, or check on Mac or Linux using the following command:
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 172.25.165.208 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:d7e8:c5fe:5ab:6528%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): {83.234.8.204, 129.185.103.222}
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 4b:0c:0f:18:93:83
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 d3:66:cb:37:00:c7
}
Resolving Connection Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.8, 11.1.7, or 12.2.7, there are various troubleshooting tools available. However, these tools do not provide a set of correlated values over time, which can be a limitation. This is where automated remote troubleshooting becomes beneficial, especially for teams engaging in remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool offers a comprehensive range of logs, although much of it is specific to point-in-time wireless issues like wdutil.
To run it in the background and generate logs, use the command sudo nohup /usr/bin/sysdiagnose -u &, which writes logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose, but be cautious of the large file sizes, typically around 300MB.
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