How To Understand Apple No-access
Understanding Internet Addressing
When it comes to the Internet, you may be assigned a Public IPv4 address such as 82.168.124.198 or an IPv6 address like 2000:cf5:40d6:c00d:c9f0:19c8:d876:5d0f. You can verify your assigned address by visiting https://test-ipv6.com/. However, explaining these addresses to individuals who are not well-versed in technology, or even mentioning MAC addresses like 15:09:05:c8:30:5c, can lead to errors and complexities. Furthermore, this information does not provide any historical context, particularly when dealing with previous issues.
Navigating the World Wide Web
In order to access a website such as https://friesen.com, your device first contacts a DNS server to translate the host portion (friesen) along with the Top Level Domain (com) of the URL, into an IP address such as 181.25.79.119. Whenever your computer sends web requests, it also includes information about its type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Significance of Default Gateways
Typically, your default gateway is automatically configured via DHCP and is assigned an address like 192.168.60.115 (often ending in .1 or .254 based on the scope size), to which your computer sends all its traffic to be routed onwards. For more information on troubleshooting IPv6 connectivity, you can refer to our detailed guide on how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux systems, you can verify this using the following 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 192.168.60.115 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:ed4e:9f57:2015:4791%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): {226.3.237.102, 124.222.194.246}
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 15:09:05:c8:30:5c
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 e8:2d:51:86:ab:35
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data at the physical and data layers, users have the option of using a wired or wireless (Wi-Fi) medium to send data to the router.
Strategies for Addressing Problems on Apple macOS / OSX
Irrespective of the version of OSX or macOS being used, whether it’s 10.12.1, 11.3.1, or 12.0.4, there are various troubleshooting tools available. However, these manual actions and scripts do not offer a series of correlated values over time. This is where automated remote troubleshooting becomes particularly relevant, especially for teams that have adopted remote work and the concept of Work From Anywhere (WFA).
Pre-Installed Scripts for Assistance
A highly valuable tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings in the CLI and can be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz for the user. If preferred to be run interactively (although there isn’t much interaction), users can execute sudo /usr/bin/sysdiagnose, which will display a privacy warning. When not run in the background, it should open Finder in the correct location, or users can navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. It’s important to be mindful of the file sizes, which are approximately 300MB more or less.
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