How To Test MacOS No-access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 228.26.204.140 or an IPv6 address like 2000:44fd:89bb:b981:d873:464b:8771:1f45. You can verify this information through the https://test-ipv6.com/ website. However, explaining these addresses to individuals who are not technically inclined can be prone to errors and can become complex, especially when dealing with MAC addresses like 98:3f:f0:67:f1:5a. Furthermore, this method does not provide any historical data, especially when addressing past issues.
Navigating the World Wide Web
In order to access a website such as https://hilll-shields.io, you must first contact a DNS server to translate the host portion (hilll-shields) in combination with the Top Level Domain (io) of the URL, into an IP address such as 38.90.79.2. Whenever your computer and browser make web requests, they also include information about their type, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
The default gateway for your system is typically an address that is automatically configured through DHCP. This address may be something like 10.146.5.56 (although they typically end in .1 or .254, depending on the scope size). Your computer directs all of its traffic to this default gateway to be properly routed. For those interested in learning more about IPv6, a more in-depth discussion can be found at how-to-fix-ipv6-connectivity/. Alternatively, you can check this information on Mac or Linux systems using the following command:
route -n
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 10.146.5.56 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 fe80:7bba:cdb9:2921:5abb%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): {63.29.252.103, 121.33.80.202}
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 98:3f:f0:67:f1:5a
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 b5:87:e6:06:12:a8
}
Resolving Connectivity Issues with 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 Solutions for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.15.2, 11.5.3, or 12.3.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where the significance of automated remote troubleshooting becomes evident, particularly for teams that are engaged in remote work and Work From Anywhere (WFA).
Effective Built-in Scripts
One valuable tool in 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. Furthermore, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is only related to wireless settings at a specific time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. For an interactive run, you can execute sudo /usr/bin/sysdiagnose, which comes with a privacy warning. If not run in the background, it should open Finder in the correct location or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. However, note that the file sizes are approximately 300MB.
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