How Do You Understand Common Wifi No Access
Understanding the Functioning of Internet Addresses
When using the Internet, individuals may be assigned a Public IPv4 address such as 252.207.233.53 or an IPv6 address like 2000:660f:a35d:9cf7:c7e3:21a4:9175:6975. It is possible to verify this information from https://test-ipv6.com/. However, conveying such addresses, as well as MAC addresses like 43:c4:fe:25:07:77, to those without technical expertise can be prone to errors and complications. Moreover, this method does not provide historical data, particularly from previous issues.
Navigating the World Wide Web
To access a website such as https://leuschke-herzog.net, the first step involves reaching out to a DNS server to convert the host portion (leuschke-herzog) in combination with the Top Level Domain (net) of the URL, into an IP address like 62.155.220.36. When making web requests, your computer and browser actually transmit their type, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
By default, the gateway is typically an address configured automatically via DHCP. An example of a default gateway is 192.0.0.175 (although they often end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed onward. For IPv6, we offer an in-depth guide on how-to-fix-ipv6-connectivity/, although you can perform a check on Mac or Linux with:
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 192.0.0.175 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 fe80:7a1a:1fe4:4dea:11cb%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): {6.71.229.227, 196.253.145.244}
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 43:c4:fe:25:07:77
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 d5:36:1e:fa:1b:68
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Steps for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.15.3, 11.1.6, or 12.1.9, there are several tools available for resolving issues. However, these tools do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes beneficial, especially for teams engaged in remote work and Work From Anywhere (WFA).
Useful Built-in Tools for Troubleshooting
One valuable tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings to the command-line interface and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although most of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, use the commandsudo nohup /usr/bin/sysdiagnose -u &. For an interactive run (although there is not much interaction), use the commandsudo /usr/bin/sysdiagnose and it will provide a privacy warning. When run in the foreground, 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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