How To Fix Common Wifi No Access
Understanding IP Addressing
When using the Internet, you are assigned an IP address, such as 175.103.2.98 for IPv4 or 2000:2827:e78f:770f:bc7e:15e:b2eb:c75e for IPv6. To verify your IP address, you can visit https://test-ipv6.com/. However, communicating these addresses, and even calling out MAC addresses like 35:96:42:0d:5c:40, can be prone to errors, especially for those who are not tech-savvy. Furthermore, this method does not provide any historical data, particularly when dealing with past issues.
Navigating the Internet
Accessing a website such as https://nicolas-walter.org involves contacting a DNS server to convert the host portion (nicolas-walter) and the Top Level Domain (org) of the URL into an IP address, such as 156.129.124.9. Each web request from your computer and browser contains information about its type, for example, Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding Default Gateways
The default gateway is typically an automatically configured address through DHCP. You are assigned a default gateway, such as 10.190.238.66 (which typically ends in .1 or .254 based on the scope size), and this is where your computer directs all its traffic to be routed onwards. For IPv6, a detailed explanation can be found at how-to-fix-ipv6-connectivity/, and on Mac or Linux systems you can verify 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 10.190.238.66 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:db3e:13e8:c632:c058%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): {0.222.87.170, 229.182.179.67}
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 35:96:42:0d:5c:40
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 fd:37:77:73:8c:64
}
Resolving Issues with Wired or Wireless Connections
When sending data to your router, you may utilize a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX Systems
Regardless of the version of OSX/macOS (such as 10.15.5, 11.5.6, or 12.2.5), there are various tools available for resolving issues. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams operating in remote and Work From Anywhere (WFA) settings.
In-Built Scripts to Aid Troubleshooting
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs (although much of it is only relevant to wireless settings at a specific time, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz. Alternatively, if you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will display a privacy warning. Running it in this manner will either open Finder in the correct location or allow you to navigate to /var/tmp using Finder with the Cmd+Shift+G command. It’s important to be aware of the file sizes, which can be around 300MB or more.
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