How To DiagnOSe Apple No-access
Understanding the Functionality of Internet Addressing
When using the Internet, one might be assigned a Public IPv4 address such as 227.182.126.73 or an IPv6 address like 2000:138:f6c:1895:941e:b437:4ca8:e79. A convenient way to verify this information is through https://test-ipv6.com/. However, attempting to convey these addresses to individuals who are not well-versed in technology, or even referencing MAC addresses like ec:69:b3:c9:42:d5, can be prone to errors and becomes complex rather rapidly. Furthermore, this method does not provide any historical data, particularly from previous occurrences of issues.
Navigating the World Wide Web
When attempting to visit a webpage such as https://raynor.co, the initial step involves accessing a DNS server in order to translate the host portion (raynor) combined with the Top Level Domain (co) of the URL into an IP address, such as 252.55.87.77. As a matter of fact, your computer and browser include the web request type in all web requests, 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
Recognizing the Significance of Default Gateways
Typically, a default gateway is an automatically configured address obtained through DHCP. It is common to receive a default gateway such as 10.41.205.193 (although they often end in .1 or .254 depending on the scope size), and this is where your computer transmits all of its traffic to be routed onward. Additionally, for IPv6, we have an in-depth analysis located at how-to-fix-ipv6-connectivity/. However, on Mac or Linux systems, you can verify this 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 10.41.205.193 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 2106:f683:7c:cdbf:4873:5b55:fe45:88e5%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): {50.151.52.88, 96.101.170.125}
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 ec:69:b3:c9:42:d5
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 bb:d8:5b:58:6b:7e
}
Fixing Connectivity Issues for Wired or Wireless Networks
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are on OSX/macOS version 10.14.7, 11.0.7, or 12.2.3, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, which is crucial for remote troubleshooting, especially for teams working remotely or from anywhere.
Useful Built-in Tools and Scripts
One incredibly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the command line interface (CLI) of current wireless related settings and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz, while running sudo /usr/bin/sysdiagnose interactively (despite minimal interaction) will give a privacy warning and open Finder in the correct location. However, beware of the large file sizes of approximately 300MB.
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