How Do You Fix Mac No-access
The Functioning of Internet Addressing
When using the Internet, individuals may be assigned either a Public IPv4 address, such as 170.116.221.16, or an IPv6 address like 2000:9af4:7b9f:9e6d:3406:7f33:8c28:9db1. Verification of this can be done at https://test-ipv6.com/. However, for those without technical expertise, conveying and handling these addresses can quickly become complicated and prone to errors. Furthermore, these addresses do not provide any historical data, particularly from previous incidents.
Navigating the Internet
In order to reach a website like https://schmidt.org, the first step is to access a DNS server to convert the host part (schmidt) combined with the Top Level Domain (org) of the URL into an IP address, such as 241.43.227.221. When making web requests, the type of computer and browser are included, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.
The Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. A default gateway, such as 192.0.0.40 (although typically ending in .1 or .254 depending on the scope size), is where the computer sends all of its traffic to be routed. For IPv6, a thorough explanation can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, the gateway can be checked 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 192.0.0.40 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:f14b:c5b5:9668:c9b7%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): {77.120.13.110, 154.218.226.76}
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 69:f6:59:49:f1:a6
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 2b:d3:5f:e0:81:58
}
Resolving Issues with Wired and Wireless Connections
When transmitting data to your router, it’s essential to troubleshoot any issues that may arise at the physical and data layer, whether you’re using a wired or wireless (Wi-Fi) medium.
Solutions for Apple macOS / OSX Users
Regardless of whether you are using 10.12.6, 11.6.7, or 12.1.1, there are various tools available for troubleshooting on your Apple macOS / OSX system. However, manually executing these actions and scripts does not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are engaged in remote work and Work From Anywhere (WFA).
Leveraging Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings in the CLI and can also be configured to generate specific logs for troubleshooting. Another, more comprehensive tool is the sysdiagnose tool, which can generate a wide range of logs related to wireless (although many are point-in-time logs, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. For those who prefer to run it interactively, running sudo /usr/bin/sysdiagnose will prompt a privacy warning and 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 are approximately 300MB.
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