How Do You Support Wifi No Access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 177.1.130.56 or an IPv6 address like 2000:c93e:6baa:c7d2:cbbd:7da0:3dc2:3753. A simple way to verify this is by visiting https://test-ipv6.com/. However, conveying these addresses, or even referencing MAC addresses like ae:91:3a:39:c6:34, can be error-prone and complicated for non-technical individuals. Furthermore, this method lacks historical data, particularly for addressing previous problems.
Navigating the World Wide Web
Accessing a web page like https://yost.name involves initially connecting to a DNS server to convert the combination of the host portion (yost) and the Top Level Domain (name) of the URL into an IP address, such as 248.59.45.183. Notably, your computer and browser transmit its type with every web request, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address obtained via DHCP, such as 10.219.108.190 (usually ending in .1 or .254 depending on the scope size). This is where your computer directs all its traffic to be routed onwards. For IPv6, an in-depth guide on how-to-fix-ipv6-connectivity/ is available, and the settings can be verified on Mac or Linux 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 10.219.108.190 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 fe80:44c5:d641:ca64:3268%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): {117.86.185.248, 121.22.37.209}
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 ae:91:3a:39:c6:34
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 2c:fa:91:32:a8:c9
}
Addressing Wired and Wireless Connection Issues
When it comes to transmitting data to your router, you could be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX
Regardless of the version of OSX/macOS you’re using - be it 10.12.6, 11.5.9, or 12.3.5, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing In-Built Scripts
An extremely useful tool on OSX/macOS is the sudo wdutil info which provides a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose which can generate a wide range of logs, although many are only related to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, for an interactive run (although there isn’t much interaction), use sudo /usr/bin/sysdiagnose and follow the 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 or use Finder to point to the path. Keep in mind that the file sizes are approximately 300MB.
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