How Do You Fix MacOS No-access
Functionality of Internet Addressing
When connected to the Internet, you are assigned a Public IPv4 address, such as 139.153.71.193, or an IPv6 address, such as 2000:c703:66c:51f2:a2f8:4f3f:80a4:8970. Verification of these addresses can be done at https://test-ipv6.com/, however, conveying or referencing MAC addresses like 50:24:e1:20:42:d4 to individuals less knowledgeable in technology can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data on previous issues.
Navigating the World Wide Web
When attempting to visit a webpage, such as https://romaguera.org, the initial step involves accessing a DNS server to convert the host portion (romaguera) in combination with the Top Level Domain (org) of the URL into an IP address, for example, 166.238.115.150. Additionally, your computer and browser transmit their type along with all web requests, as shown by:
Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Defining Default Gateways
Typically, your default gateway is automatically configured via DHCP and is assigned an address like 10.26.9.85 (usually ending in .1 or .254 based on the scope size). This address serves as the location where your computer sends all of its traffic to be routed onwards. For a comprehensive guide on fixing IPv6 connectivity, refer to how-to-fix-ipv6-connectivity/. On Mac or Linux, the gateway can be checked using the following code:
ifconfig | grep "inet " | grep -v 127.0.0.1
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 10.26.9.85 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:f814:1beb:ec5c:69ef%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): {8.163.154.186, 97.85.51.101}
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 50:24:e1:20:42:d4
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 e7:c3:a9:8e:5b:24
}
Resolving Issues with Wired and Wireless Connections
When it comes to sending data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Users
Regardless of which version of OSX/macOS you are operating on, whether it’s 10.12.6, 11.2.6, or 12.2.1, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes incredibly valuable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) model.
Useful Built-in Scripts
A very handy tool found on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
To run it in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run (though there is minimal interaction), use sudo /usr/bin/sysdiagnose, which will trigger 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 Cmd+Shift+G in Finder. However, it’s important to be aware of the large file sizes, which are approximately 300MB.
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