How Can I Support MacOS IP Settings
The Functioning of Internet Addressing
When using the Internet, you are provided with a Public IPv4 address such as 203.2.169.114 or an IPv6 address like 2000:f236:f2d:a0e5:d17c:912d:3524:7bb5. You can verify this by visiting https://test-ipv6.com/. However, translating these addresses for non-technical individuals can be challenging, and the same applies to MAC addresses like 62:dd:e2:0c:2f:76 without any historical context.
Navigating the World Wide Web
In order to access a website like https://wuckert-cassin.net, the first step is to request the translation of the host portion (wuckert-cassin) combined with the Top Level Domain (net) of the URL into an IP address such as 253.181.45.48. Furthermore, your computer and browser transmit their type with 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
The default gateway is typically an address that is automatically configured via DHCP. This address, such as 172.19.106.152 (often ending in either .1 or .254 based on the scope size), is where your computer sends all its traffic to be routed onwards. For IPv6, a comprehensive guide is available 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 172.19.106.152 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:a2d4:fb2b:734b:e539%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): {156.10.221.191, 164.145.222.14}
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 62:dd:e2:0c:2f:76
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 51:77:6b:9e:5e:df
}
Resolve Issues with Wired and Wireless Network Connections
When it comes to transmitting data, you may use either a wired or wireless (Wi-Fi) medium at the physical and data layer to send the data to your router.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, such as 10.14.4, 11.1.1, or 12.2.2, there are various tools available for resolving issues. However, these tools and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes beneficial, especially for teams that adopt remote work and Work From Anywhere (WFA).
Utility Scripts for Assistance
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. Moreover, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are only relevant to wireless at a specific point in time, similar to wdutil.
The command sudo nohup /usr/bin/sysdiagnose -u & can run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz. For interactive use (though it does not require much interaction), 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. Keep in mind that the file size is around 300MB or thereabouts.
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