How Can I Test OSX No-access
Understanding the Function of Internet Addressing
When accessing the Internet, individuals may be assigned a Public IPv4 or IPv6 address. This can be verified by visiting https://test-ipv6.com/. However, communicating these addresses, as well as MAC addresses, can be complex, particularly for those who are not tech-savvy. Moreover, this method does not provide any historical data, especially for past issues.
The Process of Navigating the Web
In order to visit a specific web page, such as https://kihn-little.com, the user’s computer first interacts with a DNS server to translate the URL’s host and Top Level Domain to an IP address. This IP address is what the computer and browser send along with every web request, specifying the type and other details.
Understanding the Significance of Default Gateways
The default gateway is typically an automatically assigned address obtained through DHCP. This gateway serves as the designated location where a computer sends all of its outgoing network traffic to be routed onwards. For those using IPv6, detailed information on this process can be found at how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux, users can check their default gateway.
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 10.217.154.132 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 fe80:7668:abf2:b086:3bf4%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): {181.233.232.214, 199.45.233.239}
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 2a:fe:56:75:26:82
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 dc:1e:a2:80:97:38
}
Solutions for Troubleshooting Wired and Wireless Connectivity
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.
Steps for Resolving Issues on Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.13.7, 11.2.8, or 12.2.2, 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 automated remote troubleshooting becomes essential, especially for remote work and Work From Anywhere (WFA) teams.
Useful Built-in Scripts
A useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are only point-in-time related to wireless, 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, you can use the command: sudo /usr/bin/sysdiagnose, but be cautious of the large file sizes, typically around 300MB.
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