How Can I DiagnOSe MacOS No-access
Understanding Internet Addressing
When you connect to the Internet, you will receive a Public IPv4 address or an IPv6 address. It is possible to verify this using a site like https://test-ipv6.com/. However, trying to communicate these addresses, as well as MAC addresses, can be cumbersome for those who are not tech-savvy. Furthermore, this information does not provide any historical data.
Navigating the Internet
Accessing a website involves contacting a DNS server to translate the host and Top Level Domain of the URL into an IP address. Furthermore, with every web request, your computer and browser send its type, such as Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36.
The Significance of Default Gateways
By default, your computer configures an address for the default gateway via DHCP, where all traffic is routed. For IPv6, more in-depth information can be found at how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux, this information can be checked.
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 192.0.0.217 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 fe80:34f9:e7b0:5d65:28f0%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): {83.177.1.39, 20.243.218.197}
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 88:d2:86:a6:67:24
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 43:29:a3:1f:77:a5
}
How to Troubleshoot and Resolve Connectivity Issues
When it comes to transmitting data to your router, you have the option of using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Users
No matter which version of OSX or macOS you are currently using, whether it be 10.14.5, 11.0.6, or 12.0.5, there are various troubleshooting tools available. However, these tools and manual actions may not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).
In-Built Tools for Assistance
A highly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of the current wireless settings and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be utilized to produce a wide range of logs, although much of it is only related to wireless settings and is point-in-time information, similar to wdutil.
To run the sysdiagnose tool in the background and have it 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, although this will prompt 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. Be mindful of the file sizes, which can be around 300MB more or less.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
