How To Fix OSX No-access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address like 209.27.251.169 or an IPv6 address like 2000:8d8a:c16:f4e6:eb95:46d5:85b2:38d3, which can be verified at https://test-ipv6.com/. However, explaining these addresses to non-technical individuals, or even referring to MAC addresses like 13:d5:a4:b8:9c:4b, can be error-prone and complex. Moreover, it does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
Accessing a webpage such as https://wyman-wehner.info involves initially reaching a DNS server to translate the host portion (wyman-wehner) combined with the Top Level Domain (info) of the URL into an IP address like 93.241.34.173. Your computer and browser send their type with every web request, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Role of Default Gateways
The default gateway is typically an automatically configured address via DHCP, such as 192.168.68.163 (often ending in .1 or .254 depending on the scope size). This is the location where your computer sends all its traffic to be routed onwards. For IPv6, detailed instructions can be found in the article how-to-fix-ipv6-connectivity/, or it can be checked on Mac or Linux using the command:
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 192.168.68.163 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:e41e:46d2:c113:9692%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): {249.213.191.63, 233.201.69.38}
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 13:d5:a4:b8:9c:4b
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 73:1b:34:53:b8:77
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX Users
No matter which version of OSX/macOS you are currently using, whether it’s 10.15.3, 11.3.9, or 12.3.7, there are various tools available for troubleshooting. However, these manual actions and scripts may not provide a series of correlated values over a period of time. This is where automated remote troubleshooting becomes valuable, particularly for teams that practice remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless settings at a specific point in time, similar to 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 (even though there isn’t much interaction), you can use sudo /usr/bin/sysdiagnose, which will provide 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. Just be cautious of the file sizes, which are approximately 300MB.
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