How To Test Common Wifi No Access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 242.181.212.129 or an IPv6 address like 2000:9264:b6ef:2389:31a1:a9d2:b863:dc3c. To verify your address, visit https://test-ipv6.com/. Communicating these addresses, or even mentioning MAC addresses like 0d:fa:39:d1:41:76, can be challenging and error-prone, especially for those who are not technically inclined. Moreover, it does not provide any historical data, particularly when dealing with past issues.
Navigating the World Wide Web
Accessing a web page, such as https://lakin.biz, involves initially contacting a DNS server to convert the host portion (lakin) and the Top Level Domain (biz) of the URL into an IP address, like 168.115.34.139. Your computer and browser sends 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 via DHCP. This address, such as 172.19.232.234 (usually ending in .1 or .254 based on the scope size), is where your computer directs all of its traffic to be routed onwards. For IPv6, we have an in-depth discussion on how-to-fix-ipv6-connectivity/, and you can check 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 172.19.232.234 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:c8f2:9caf:84a0:7d65%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): {127.168.243.253, 230.128.92.167}
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 0d:fa:39:d1:41:76
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 8d:f3:a9:bc:90:2d
}
Fixing Connectivity Issues on Wired and Wireless Networks
When it comes to sending data to your router, you might 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 are running, whether it’s 10.13.3, 11.0.5, or 12.0.1, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI 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 much of it is only related to wireless settings at a specific point in time, just like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp manually or use Finder with Cmd+Shift+G to navigate to the path. It’s important to note that the file sizes are approximately 300MB.
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