Understand Wifi No Access
Understanding Internet Protocol Addressing
When it comes to the internet, you might be assigned a Public IPv4 address such as 169.28.138.124 or an IPv6 address like 2000:8810:e853:ea77:d6f8:49e9:805:362f. Verifying this information can be done at https://test-ipv6.com/. However, for those who are not well-versed in technology, relaying these addresses or MAC addresses such as 50:d4:64:42:e9:e3 can lead to errors and unnecessary complexity. Additionally, such information does not provide any historical context, especially when past issues occurred.
Navigating Through the Internet
When attempting to access a website like https://stracke.org, the first step is to connect with a DNS server to convert the host portion (stracke) along with the Top Level Domain (org) of the URL to an IP address like 85.236.218.117. It’s worth noting that your computer and browser send their type with every web request, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
The Significance of Default Gateways
By default, your gateway is typically an address that is automatically configured via DHCP. This default gateway could be something like 192.168.238.202 (commonly ending in .1 or .254 based on the scope size), and it’s where your computer directs all of its traffic to be further routed. For IPv6, a comprehensive guide on how-to-fix-ipv6-connectivity/ is available, but on Mac or Linux, the status can be checked using:
command-goes-here
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 192.168.238.202 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:e646:c614:9d37:8f18%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): {106.233.134.28, 98.251.3.183}
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 50:d4:64:42:e9:e3
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 a3:9d:48:26:1a:fb
}
Troubleshooting Connectivity Issues for Wired and Wireless Network
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.
Effective Solutions for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.11.4, 11.6.7, or 12.3.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that are transitioning to remote work and embracing Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool is quite valuable as it provides a dump of the current wireless settings to the Command Line Interface (CLI), and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool is even more comprehensive as it can generate a wide range of logs, although most are point-in-time only in relation to wireless, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /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, which will give 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 approximately 300MB.
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