How Do You Check Mac No-access
The Functioning of Internet Addressing
When using the internet, individuals may have a Public IPv4 address such as 234.238.30.4 or an IPv6 address such as 2000:b7d9:4c1c:48b:82df:3e8e:b7cf:540d. This information can be verified through https://test-ipv6.com/. However, communicating these addresses to those who are not tech-savvy or even mentioning MAC addresses like d9:ca:97:ce:f3:57 can quickly become complex and prone to errors. Moreover, this method does not provide historical data, especially for past issues.
Navigating the Internet
In order to access a website like https://roob-bergnaum.info, the first step is to access a DNS server to convert the host portion (roob-bergnaum) along with the Top Level Domain (info) of the URL into an IP address like 204.6.185.185. When making web requests, your computer and browser also transmit its type, such as 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 Primary Gateways
The default gateway is typically an address that is automatically configured via DHCP. This default gateway, such as 10.32.16.7 (often ending in .1 or .254 based on the scope size), is where your computer sends all its traffic to be routed onward. For matters related to IPv6, there is an in-depth guide available at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify this information with 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 10.32.16.7 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:a29f:2aca:2866:2764%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): {130.67.160.188, 73.16.195.237}
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 d9:ca:97:ce:f3:57
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 2f:5c:7b:1d:79:31
}
Troubleshooting Issues with Wired and Wireless Connectivity
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium, operating at the physical and data layer.
Resolving Problems on Apple macOS / OSX Systems
No matter which version of OSX/macOS you are currently running - whether it’s 10.14.7, 11.2.5, or 12.0.9 - there are various tools available for troubleshooting. However, manual actions and scripts alone do not provide a consistent set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have embraced remote work and the concept of Work From Anywhere (WFA).
Useful Built-in Scripts for Mac
An extremely handy tool available on OSX/macOS is sudo wdutil info, 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 sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although much of it is only point-in-time data in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive option (although there is minimal interaction), you can run sudo /usr/bin/sysdiagnose. It will issue a privacy warning and either open Finder in the correct location or allow you to navigate to /var/tmp. Alternatively, you can use Finder with Cmd+Shift+G to point Finder to the path. Be aware that the file sizes are typically around 300MB.
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