How To Test Wifi No Access
Understanding the Functionality of Internet Addresses
When using the Internet, you are assigned a Public IPv4 address, such as 130.249.88.81 or an IPv6 address like 2000:d2d:5581:eb3c:df93:7a77:8df9:2337. You can verify this information by visiting https://test-ipv6.com/. However, for individuals who are not familiar with technical jargon, communicating these addresses or even identifying MAC addresses like bd:2a:20:01:ca:3c can lead to errors and complexity. Moreover, this method does not provide historical data, especially pertaining to past issues.
Navigating Through the World Wide Web
When attempting to access a web page, such as https://lemke.co, your first step involves reaching out to a DNS server to convert the host portion (lemke) combined with the Top Level Domain (co) of the URL into an IP address, such as 177.240.120.212. Additionally, your computer and browser transmit their type with all web requests, for example: `Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
The default gateway is typically an address that is automatically configured via DHCP. As a result, you obtain a default gateway, such as 192.0.0.86 (although they typically end in .1 or .254 based on the scope size), where your computer directs all of its traffic to be routed onwards. For IPv6, a comprehensive explanation is available in our blog post titled how-to-fix-ipv6-connectivity/. However, on Mac or Linux, you can check this by:
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 192.0.0.86 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:b33c:2f8:1eec:ba2f%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): {8.66.124.20, 46.224.249.128}
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 bd:2a:20:01:ca:3c
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 2a:74:7b:f4:5a:94
}
Fixing Network Connectivity Issues
When it comes to transferring data to your router, you may encounter issues related to the physical and data layer. These issues can arise whether you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting Solutions for Apple’s macOS
Regardless of whether you are using OSX or macOS, be it version 10.11.6, 11.4.3, or 12.1.5, there are various tools available to help troubleshoot network connectivity. However, manual actions and scripts do not provide a complete set of correlated values over time. This is where automated remote troubleshooting becomes crucial, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A very useful tool for troubleshooting on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the command line interface. This tool can also be configured to generate specific logs for troubleshooting purposes. Moreover, the sysdiagnose tool can be used to generate a wide range of logs, although much of the information is only relevant to a specific point in time, similar to the wdutil tool.
To run the sysdiagnose tool in the background and save the logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run the tool interactively by using 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 the path /var/tmp using Finder with the shortcut Cmd+Shift+G. However, be cautious of the file sizes, which can be around 300MB.
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