Understand Common Wifi Issues
How IP Addresses are Utilized on the World Wide Web
When using the Internet, individuals are assigned with either a Public IPv4 or IPv6 address. The former may look like 246.47.29.157 while the latter may look like 2000:8a4f:5448:89bf:51d:596a:d871:4fb0. It is possible to verify these addresses at https://test-ipv6.com/. However, these lengthy alphanumeric combinations can easily lead to errors and confusion among non-technical users. To add to this, such addresses do not contain historical data, making it difficult to troubleshoot past issues.
Navigating Web Pages
When trying to access a website, like https://reinger.co, the process begins by consulting a DNS server to convert the URL’s host section (reinger) along with the Top Level Domain (co) into an IP address such as 80.111.81.248. Notably, each web request from your computer and browser includes its specification. For example, Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16 denotes the browser type.
Significance of Default Gateways
In most cases, the default gateway is automatically configured through DHCP, and commonly ends with .1 or .254. For instance, a typical default gateway address could be 10.34.149.171 - the central point through which all network traffic from your computer is directed. More detailed instructions on checking the default gateway for IPv6 connectivity can be found at how-to-fix-ipv6-connectivity/, and this can also be verified on Mac or Linux systems.
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 10.34.149.171 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:e251:bb20:ed95:be38%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): {132.245.168.231, 224.91.19.88}
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 be:23:d3:3f:07:2b
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 9c:ba:4d:9f:ab:f7
}
How to Resolve Issues with Wired and Wireless Connections
When sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Step-by-Step Guide for Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you have - whether it’s 10.12.1, 11.4.1, or 12.2.5 - there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where remote troubleshooting automation becomes essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A highly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only related to wireless at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive (although not very interactive) experience, run sudo /usr/bin/sysdiagnose and heed the privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Cmd+Shift+G in Finder. Keep in mind that the file sizes are approximately 300MB.
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