How Can I DiagnOSe Mac No-access
Understanding How Internet Addresses Function
When using the Internet, individuals may be assigned a Public IPv4 address, such as 141.56.94.62, or an IPv6 address, such as 2000:305c:d261:d918:386e:8e9a:e3d4:df8c. This information can be verified through https://test-ipv6.com/. However, for those who are not well-versed in technology, conveying these addresses, or even referencing MAC addresses like 32:40:97:34:1d:0e, can become error-prone and complex. Moreover, this method does not provide historical data, particularly from past occurrences of problems.
Navigating the World Wide Web
When attempting to visit a website, such as https://hyatt.net, the first step involves accessing a DNS server to convert the host section (hyatt) in conjunction with the URL’s Top Level Domain (net) into an IP address, like 104.234.62.167. Upon making web requests, your computer and browser disclose essential information, for example, 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 gateway is typically assigned an automatically configured address through DHCP. This default gateway, such as 192.0.0.103 (commonly ending in .1 or .254 based on the scope size), is the destination where your computer directs all its traffic to be forwarded. For IPv6, a detailed guide on how-to-fix-ipv6-connectivity/ is available, while checking on Mac or Linux is achievable 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 192.0.0.103 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 fe80:5a55:c9d3:6779:b8de%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): {173.5.161.5, 54.112.155.123}
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 32:40:97:34:1d:0e
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 45:9a:c8:0f:96:05
}
Solutions for Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you could be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Connectivity Problems on Apple macOS / OSX
No matter which version of OSX/macOS you’re running, whether it’s 10.14.2, 11.3.7, or 12.2.3, there are several troubleshooting tools available. However, these manual actions and scripts don’t provide a series of connected values over time. For this reason, automated remote troubleshooting becomes essential, especially for teams that operate remotely or practice Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool offers a concise dump of current wireless settings to the CLI, and can also be customized to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs related to wireless, although many of these are only point-in-time logs, 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 &. Alternatively, for an interactive experience (with minimal interaction), use the command sudo /usr/bin/sysdiagnose which will provide 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. Keep in mind that the file sizes are typically around 300MB.
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