How To Check Apple No-access
Explanation of Internet Addressing
When using the Internet, it is common to receive a Public IPv4 address such as 198.197.205.81 or an IPv6 address like 2000:485b:fc57:238c:c7cd:12a:84a3:849. To verify this, one can visit https://test-ipv6.com/. However, communicating these addresses to individuals who are not technologically inclined, or even mentioning MAC addresses like 02:f0:7e:3d:af:65, can lead to errors and cause confusion. Moreover, it fails to provide any historical data regarding past issues.
Navigating the World Wide Web
Accessing a webpage such as https://sawayn.co entails initially accessing a DNS server to translate the host portion (sawayn) combined with the Top Level Domain (co) of the URL into an IP address, such as 151.24.10.196. With every web request, your computer and browser send their type, as indicated by the code:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateways
The default gateway is usually an automatically configured address via DHCP, resulting in a default gateway like 192.168.16.154 (but typically ending in .1 or .254 depending on the scope size). This is where your computer sends all of its traffic to be routed onwards. To learn more about IPv6, refer to our in-depth explanation on how to resolve issues with IPv6 connectivity. Meanwhile, Mac or Linux users can check by using the following:
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 192.168.16.154 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:bd90:547:9b1b:b420%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): {141.72.74.138, 212.193.244.59}
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 02:f0:7e:3d:af:65
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 23:c4:af:d2:47:db
}
Resolve Network Connectivity Issues
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX or macOS versions such as 10.14.2, 11.4.9, or 12.2.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting proves to be valuable, especially for teams that are accustomed to remote work and Work From Anywhere (WFA).
Useful Built-in Commands
One particularly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless related settings and can also 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 at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, the command sudo /usr/bin/sysdiagnose will issue a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. It’s important to be aware of the file sizes, which are typically around 300MB.
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