How To Support MacOS No-access
The Functionality of Internet Addressing
In the realm of the internet, individuals are assigned with distinctive Public IPv4 and IPv6 addresses, such as 119.155.200.136 and 2000:316c:ce08:9b8c:e376:6083:dc89:e549. The confirmation of these addresses can be verified through https://test-ipv6.com/. However, the complexity arises when attempting to communicate these addresses to those who lack technical expertise, or when identifying MAC addresses like d8:c0:78:77:4c:4a, particularly in the historical context.
Navigating Web Content
Upon seeking access to a web page such as https://steuber.org, the initial step involves interacting with a DNS server in order to translate the combination of the host portion (steuber) and the Top Level Domain (org) of the URL into an IP address, such as 8.164.189.231. Notably, all web requests from your computer and browser are accompanied by a distinct type specification, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
By and large, your default gateway is automatically assigned via DHCP, typically culminating in an address such as 172.27.172.182 (though usually ending in .1 or .254, depending on the scope size). This designated address serves as the central point through which all traffic from your computer is forwarded. For individuals seeking further insight on IPv6, a comprehensive guide is available at how-to-fix-ipv6-connectivity/, with specific reference to the Mac or Linux platforms.
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 172.27.172.182 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 fe80:2add:6618:3359:16c0%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): {132.248.219.204, 6.144.247.138}
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 d8:c0:78:77:4c:4a
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 29:67:85:ac:7d:df
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, you may utilize either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Techniques for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS version 10.12.7, 11.5.6, or 12.2.2, there are various tools available for troubleshooting. Unfortunately, these manual actions and scripts do not provide a 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) culture.
Effective Built-in Scripts
One of the useful tools on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI, and can also generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings just like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose, but beware of the large file sizes of about 300MB more or less.
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