How Do You Support MacOS No-access
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 110.105.162.91 or an IPv6 address like 2000:1f3d:a933:dc8b:187a:18a4:9f76:a0f6. The process of communicating these addresses, or even mentioning MAC addresses like d6:9a:19:ea:7c:14, can be complex and error-prone, especially for those who are not tech-savvy. Moreover, these addresses do not provide any historical data, making troubleshooting past issues difficult.
Navigating the World Wide Web
When accessing a website like https://balistreri-hilll.co, your computer first contacts a DNS server to convert the host portion (balistreri-hilll) along with the Top Level Domain (co) of the URL into an IP address, such as 48.188.174.55. Furthermore, every web request from your computer and browser includes information about their types, such as 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
The default gateway, typically obtained through automatic configuration via DHCP, is the address used by your computer to route all its outgoing traffic. This address, such as 192.168.16.229 (usually ending in .1 or .254 based on the scope size), is essential for internet connectivity. For those using IPv6, a comprehensive guide on how to address connectivity issues can be found at how-to-fix-ipv6-connectivity/. Additionally, the default gateway can be checked on Mac or Linux using:
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 192.168.16.229 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:b033:d7e3:c147:21bb%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): {208.241.255.23, 14.51.160.137}
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 d6:9a:19:ea:7c:14
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 26:ba:a1:4f:69:16
}
Solve Issues with Wired and Wireless Connections
When transferring data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are on OSX/macOS version 10.15.4, 11.6.1, or 12.0.9, there is a variety of tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One particularly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless settings 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 much of it is related to wireless settings and is more comprehensive than wdutil.
To run the sysdiagnose tool in the background and generate logs in /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 which will give a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp manually or use Finder with the Cmd+Shift+G shortcut to point Finder to the path. Keep in mind that the file sizes are approximately 300MB or less.
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