How To Support Wifi No Access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 7.30.33.172 or an IPv6 address like 2000:43e7:37a7:2206:1598:e1af:7afb:d97a. You can verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to non-technical individuals or referring to MAC addresses like d2:d3:0c:70:52:47 can quickly become complex and prone to errors. Moreover, it does not provide any historical data, especially during previous malfunctions.
How Web Access Works
When accessing a webpage such as https://schimmel-bednar.name, you first contact a DNS server to convert the host portion (schimmel-bednar) combined with the Top Level Domain (name) of the URL into an IP address like 193.167.14.255. Your computer and browser include their types in all web requests, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
Typically, your default gateway is an address assigned automatically via DHCP. You receive a default gateway like 172.26.0.3 (commonly ending in .1 or .254 based on the scope size), and this is where your computer forwards all its traffic for further routing. For IPv6, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/, or you can check on Mac or Linux by 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 172.26.0.3 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:eda3:5782:b52f:1925%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): {114.255.61.165, 28.92.171.82}
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 d2:d3:0c:70:52:47
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 02:c9:4a:15:ac:a0
}
Solutions for Troubleshooting Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Take on Apple macOS / OSX Systems
Regardless of the version of OSX/macOS you are using, whether it’s 10.13.9, 11.0.7, or 12.2.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. For this reason, automated remote troubleshooting is particularly beneficial for teams that have embraced remote work and Work From Anywhere (WFA).
Pre-Installed Scripts for Assistance
An extremely helpful tool on OSX/macOS is sudo wdutil info, which 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 can be used to generate a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to the wdutil.
To run it in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (even though there is minimal interaction), you can use sudo /usr/bin/sysdiagnose, which will trigger a privacy warning. If 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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