Check Wifi No Access
A Primer on Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address, such as 36.149.252.36, or an IPv6 address like 2000:7e5a:e419:3a01:b145:fb78:6669:1083. You can verify this information at https://test-ipv6.com/. However, conveying these addresses to individuals who aren’t well-versed in technology, or discussing MAC addresses like 80:89:d2:2e:ad:3f, can be error-prone and complex. Furthermore, this method does not provide any historical data, especially regarding previous issues.
Navigating the World Wide Web
When accessing a webpage like https://pfannerstill.net, you first connect to a DNS server to translate the host portion (pfannerstill) combined with the Top Level Domain (net) of the URL to an IP address like 205.36.102.12. Your computer and browser actually sends its type with all web requests, for example, Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically assigned address via DHCP. You will receive a default gateway like 10.61.54.94 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, we delve into this topic further at how-to-fix-ipv6-connectivity/. You can also 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 10.61.54.94 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 fe80:11d8:701f:1479:c613%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): {41.8.62.135, 148.130.240.51}
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 80:89:d2:2e:ad:3f
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 47:0c:f4:48:f9:9b
}
Fixing Connectivity Issues with Wired and Wireless Connections
When it comes to sending data to your router, it’s important to troubleshoot and address any issues that may arise with both wired and wireless (Wi-Fi) connections at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
No matter which version of OSX/macOS you’re using, whether it’s 10.11.8, 11.1.3, or 12.2.3, there are various tools available for troubleshooting. However, these manual actions and scripts don’t provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts for Troubleshooting
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless settings, 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 relevant to wireless settings at a specific time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively with sudo /usr/bin/sysdiagnose, which will give a 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. Keep in mind that the file sizes are approximately 300MB.
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