How Can I Support MacOS No-access
Understanding the Functionality of Internet Addresses
When using the Internet, you are assigned either a Public IPv4 address such as 182.191.226.43 or an IPv6 address like 2000:eaaa:bf47:1d7b:a0c8:eaaa:c317:21ec. These can be verified at https://test-ipv6.com/. However, attempting to communicate these addresses to individuals who are not well-versed in technology, or even mentioning MAC addresses like ae:db:0c:0e:ca:fa, can lead to errors and complexity. Moreover, this does not provide any historical data, especially when previous issues occurred.
Navigating Websites
Accessing a website such as https://bednar.net begins with contacting a DNS server to translate the host portion (bednar) and the Top Level Domain (net) of the URL into an IP address like 86.192.110.72. Every web request from your computer and browser specifies its type, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
Normally, your default gateway is automatically assigned an address via DHCP, such as 172.28.212.183 (typically ending in .1 or .254 depending on the scope size). This is where all traffic from your computer is directed to be routed further. For IPv6, a comprehensive guide on how-to-fix-ipv6-connectivity/ is available, and on Mac or Linux systems, it can be verified 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 172.28.212.183 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 fe80:975d:713a:9a9a:1d8e%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): {44.234.80.94, 229.213.204.34}
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 ae:db:0c:0e:ca:fa
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 c3:9c:c4:31:e1:87
}
Troubleshooting Network Connectivity Issues
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Take for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.11.8, 11.6.7, or 12.2.4, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, which is crucial for effective troubleshooting. This is where automated remote troubleshooting shines, especially for remote work and Work From Anywhere (WFA) environments.
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info command provides a dump of current wireless settings, and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can generate a wide range of logs, although much of it is only for a specific point in time in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and generate logs at /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, although it will give a privacy warning. When not run in the background, it will 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 sizes will be around 300MB.
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