How To Test Wifi Router Issues
Demystifying Internet Addressing
When using the Internet, you are assigned a Public IPv4 address like 196.235.132.66 or an IPv6 address like 2000:13b0:244c:b106:3c29:8c8f:6331:740f. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not well-versed in technology, conveying these addresses or even referencing MAC addresses like eb:06:14:ac:e5:fc can lead to errors and complexities. Moreover, this approach does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When attempting to access a webpage such as https://kessler.co, your device firstly contacts a DNS server to convert the host portion (kessler) combined with the Top Level Domain (co) of the URL into an IP address like 214.146.46.213. Whenever your computer and browser sends its type along with all web requests e.g. Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
Understanding the Significance of Default Gateways
Typically, your default gateway is an automatically configured address via DHCP. You receive a default gateway like 172.26.111.234 (although they usually end in .1 or .254 based on the scope size) and it is the point where your computer directs all its traffic to be routed further. For IPv6, we provide an in-depth guide on how-to-fix-ipv6-connectivity/ but you can verify on Mac or Linux using the following command:
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 172.26.111.234 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:a40c:7c0d:e6f5:3522%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): {213.136.180.184, 218.115.54.185}
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 eb:06:14:ac:e5:fc
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 d5:e5:17:57:d1:30
}
Resolve Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
No matter which version of OSX/macOS you’re running - whether it’s 10.15.4, 11.2.4, or 12.1.9 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting comes in handy, especially for teams that are embracing remote work and the Work From Anywhere (WFA) concept.
Useful Built-in Scripts
One valuable tool on OSX/macOS is 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 only relevant to wireless settings, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, but be aware of the large file sizes of about 300MB.
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