How Can I Check MacOS No-access
Understanding Internet Protocol Addressing
When you connect to the internet, your device is assigned a unique Public IPv4 address, such as 251.205.251.197, or an IPv6 address, like 2000:1230:b8b5:6f29:d718:34b3:c047:a518. You can verify this information through https://test-ipv6.com/. However, attempting to convey these addresses or even referencing MAC addresses like 4c:f3:7c:ec:29:53 can be prone to errors and quickly become complex, especially for those unfamiliar with the technical aspects of the internet. Moreover, this method does not provide historical data, particularly for past issues.
Navigating the World Wide Web
When you access a website like https://rau.net, your request is first sent to a DNS server to translate the host part (rau) combined with the Top Level Domain (net) into an IP address, such as 253.145.246.53. Each web request from your computer and browser is accompanied by its type, 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
Your default gateway is typically an address automatically configured via DHCP. It usually ends in .1 or .254, depending on the scope size, and plays a crucial role as the location to which your computer forwards all its traffic for further routing. For IPv6, you can refer to our in-depth guide at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify the default gateway 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 192.168.100.2 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 fe80:4c9a:ff72:765:ff4a%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): {166.20.248.230, 148.140.246.40}
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 4c:f3:7c:ec:29:53
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 35:98:38:1e:3d:bc
}
Resolving Connectivity Issues for Wired or Wireless Networks
When it comes to transmitting data to your router, you could be utilizing a wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Irrespective of whether you are using OSX/macOS version 10.14.7, 11.0.2, or 12.2.5, there exists a variety of troubleshooting tools available. However, the manual actions and scripts do not provide a series of correlated values over time, making it challenging. This is where automated remote troubleshooting becomes essential, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A helpful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless networks, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer an interactive approach (though there is minimal interaction), you can run sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not run in the background, it should open Finder in the correct location, otherwise, you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. However, be cautious of the file sizes, which can be around 300MB.
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