How Do You Understand Apple No-access
Understanding IP Addressing
When you’re using the Internet, you receive an IPv4 address such as 149.65.86.22 or an IPv6 address like 2000:cefd:966f:917b:9c0d:d00b:a438:f58a. You can verify this information from https://test-ipv6.com/. However, attempting to convey these addresses, or even mention MAC addresses like 48:60:d8:b7:0e:87, in a way that’s understandable for non-tech individuals can be prone to errors and become complex rather quickly. Moreover, this information does not offer any historical data, particularly for previous issues.
Navigating the World Wide Web
When you want to visit a website like https://cummings.org, you first reach out to a DNS server to convert the host section (cummings) combined with the Top Level Domain (org) of the URL into an IP address like 77.57.10.41. Your computer and browser transmit their type along with every web request, 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 automatically configured address via DHCP. You receive a default gateway such as 192.168.177.149 (although they usually end in .1 or .254 based on the scope size) and this is where your computer forwards all its traffic for routing. For IPv6, you can delve deeper into how-to-fix-ipv6-connectivity/ or check on Mac or Linux with:
<br>
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 192.168.177.149 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 fe80:2554:894d:e20c:42a3%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): {158.243.205.157, 37.29.167.31}
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 48:60:d8:b7:0e:87
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 43:2c:7e:47:02:d1
}
Troubleshooting Wired and Wireless Network Issues
When it comes to transferring data to your router, you may be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX or macOS version 10.14.9, 11.1.8, or 12.0.4, there are various tools available for troubleshooting network issues. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes essential, especially for remote work and Work From Anywhere (WFA) teams.
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool is very beneficial as it provides a detailed dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs related to wireless issues, although many of these are specific to a particular point in time, similar to the wdutil tool.
To run the sysdiagnose tool in the background and generate logs at /var/tmp/<blah>.tar.gz, you can use the command: sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, to run it interactively, you can use the command: sudo /usr/bin/sysdiagnose, but be prepared for large file sizes of around 300MB.
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