Understand Common Wifi No Access
Understanding Internet Addressing
When using the Internet, your device may be assigned a Public IPv4 address such as 4.249.37.39 or an IPv6 address like 2000:218:da67:101d:161b:c4ef:8ee9:3dad. Verification of this can be done at https://test-ipv6.com/. However, conveying these addresses or even MAC addresses like b8:4e:9f:8f:b7:cf to individuals who are not technologically savvy can be prone to errors and quickly become complex. In addition, this method lacks historical data, particularly for past issues.
Navigating the World Wide Web
When attempting to access a webpage such as https://heaney.info, the first step is to contact a DNS server to translate the host name (heaney) in combination with the Top Level Domain (info) of the URL to an IP address like 170.220.59.169. It is important to note that your computer and browser include its type with each web request, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
The default gateway is typically a DHCP-configured address that the computer automatically obtains. The default gateway, such as 192.0.0.161, (often ending in .1 or .254 based on the scope size) is where the computer sends all of its traffic to be forwarded. A detailed guide on IPv6 can be found at how-to-fix-ipv6-connectivity/, while Mac and Linux users can verify using the following command:
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 192.0.0.161 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:e1c9:ab60:4940:9722%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): {160.252.36.198, 182.133.178.37}
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 b8:4e:9f:8f:b7:cf
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:ce:e0:57:e5:3e
}
Resolve Connection Issues for Wired and Wireless Networks
When it comes to transferring data to your router, you might be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
How to Troubleshoot on Apple macOS / OSX Devices
Regardless of whether you are using OSX/macOS versions such as 10.11.3, 11.6.5, or 12.0.1, there are several troubleshooting tools available. However, these tools may not provide a consistent set of interconnected values over time, especially for teams that are adapting to remote work and Work From Anywhere (WFA).
Pre-Installed Scripts for Assistance
An effective tool for troubleshooting on OSX/macOS is the sudo wdutil info, which provides a comprehensive dump of current wireless settings to the command line interface and can also be configured to generate specific troubleshoot logs. Additionally, for a more comprehensive set of logs related to wireless issues, the sysdiagnose tool can be used.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose and follow the instructions, keeping in mind the relatively large file size of approximately 300MB.
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