How To Understand Wifi No Access
The Function of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 37.7.27.217 or an IPv6 address like 2000:a3eb:c553:d490:920f:e21a:234f:89d2. The https://test-ipv6.com/ website can verify this for you. However, for those who are not tech-savvy, communicating these addresses or calling out MAC addresses like 88:e9:96:6b:e1:b1 can be prone to errors and quickly become complex. It also lacks historical data, which is important for previous problem-solving.
Navigating the Internet
When accessing a website like https://lubowitz.io, you first connect to a DNS server to translate the host portion (lubowitz) combined with the Top Level Domain (io) of the URL into an IP address such as 41.106.19.180. With every web request, your computer and browser send their types, 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
The default gateway is typically an automatically configured address via DHCP. You are given a default gateway like 10.59.129.117 (although they generally end in .1 or .254 based on the scope size), and it is where your computer directs all traffic to be further routed. For IPv6, a detailed explanation can be found on how-to-fix-ipv6-connectivity/, and you can verify this on Mac or Linux 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 10.59.129.117 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 fe80:8e02:f9c1:5a88:e32a%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): {165.18.27.176, 240.32.47.30}
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 88:e9:96:6b:e1:b1
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 36:ff:22:06:b0:d4
}
Troubleshooting Network Connectivity
When it comes to sending data to your router, you may encounter issues at the physical and data layer when using either a wired or wireless (Wi-Fi) medium.
Resolving Issues on Apple Devices
Regardless of your OSX/macOS version, whether it’s 10.14.2, 11.3.5, or 12.3.6, there are multiple tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where remote troubleshooting automation becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
In-Built Tools for Assistance
A highly useful tool on OSX/macOS is 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 troubleshooting logs. Moreover, the sysdiagnose tool offers a more comprehensive option for generating various logs, although much of the information is only relevant to the wireless aspect, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and generate logs in /var/tmp/<blah>.tar.gz. If you prefer an interactive approach (although there is minimal interaction), you can run sudo /usr/bin/sysdiagnose and it will provide a privacy warning. When not running in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder or Cmd+Shift+G. Keep in mind that the file sizes will be around 300MB.
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