How To Check Common Wifi No Access
How IP Addressing Functions
When using the Internet, you are assigned a Public IPv4 address, such as 226.110.196.130, or an IPv6 address like 2000:5ad5:b7ac:75cd:adf8:32d3:dbd9:4d8c. This information can be verified at https://test-ipv6.com/. However, conveying or referring to these addresses, including MAC addresses such as 71:b8:1d:fa:12:f9, can be prone to errors and become complicated quickly, especially for those who are not technically inclined. Moreover, this does not offer any historical data, particularly when addressing past issues.
Navigating the Internet
When accessing a webpage like https://tillman.name, the initial step is to connect to a DNS server to convert the host section (tillman) paired with the Top Level Domain (name) of the URL into an IP address, such as 40.245.215.230. With every web request, your computer and browser actually transmit its type, 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 allocated address through DHCP. You receive a default gateway, such as 192.0.0.44 (although they usually end in .1 or .254 based on the scope size), and this is where your computer directs all its traffic to be forwarded. For IPv6, detailed instructions are provided in our article on how-to-fix-ipv6-connectivity/, but you can verify this 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 192.0.0.44 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 fe80:9839:497f:48a7:6959%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): {222.73.232.184, 143.148.194.154}
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 71:b8:1d:fa:12:f9
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 bd:24:f8:7c:ba:5b
}
Resolve Connectivity Issues with Wired or Wireless Networks
When it comes to transmitting data to your router, you may utilize a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
No matter the version of OSX/macOS you are using, whether it’s 10.11.4, 11.6.5, or 12.1.4, there are various tools available for resolving connectivity issues. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One extremely helpful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings to the 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 related to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will provide a privacy warning. When 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 will be approximately 300MB.
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