How Do You Understand Common Wifi Router Issues
Understanding Internet Addressing
When using the Internet, you will be assigned a Public IPv4 address such as 167.242.87.204 or an IPv6 address like 2000:98d8:cbd1:e45f:5c15:c8f5:7868:1d64. You can verify this information at https://test-ipv6.com/. However, the challenge arises when attempting to relay these addresses to individuals who are not tech-savvy. It becomes prone to errors and quickly becomes complex. Furthermore, these addresses do not provide any historical data, especially from previous issues that occurred.
Navigating the World Wide Web
In order to access a website such as https://schmitt.net, your computer relies on a DNS server to convert the combination of the host portion (schmitt) and the Top Level Domain (net) into an IP address like 159.145.41.202. Each web request from your computer and browser includes its type, for example:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding Default Gateways
The default gateway is typically an automatically configured address provided by DHCP. It is usually assigned an address like 192.0.0.222 (ending in .1 or .254 depending on the scope size), and serves as the point where your computer routes all of its traffic. For an in-depth look at IPv6, visit our blog post on how-to-fix-ipv6-connectivity/. To check on Mac or Linux systems, use 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 192.0.0.222 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 fe80:63d:f484:6d48:e881%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): {94.237.5.221, 227.22.64.16}
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 c5:93:75:24:ac:11
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 19:1c:d5:5e:60:ec
}
Diagnosing and Resolving Connectivity Issues
When it comes to sending data to your router, you may utilize a wired or wireless (Wi-Fi) medium at the physical and data layer.
Identifying Solutions for Apple macOS / OSX
Regardless of which version of OSX/macOS you are currently using, whether it’s 10.12.2, 11.4.7, or 12.3.3, 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 proves to be particularly useful, especially for teams that have adopted remote work and Work From Anywhere (WFA).
Utilizing Pre-Installed Scripts
On OSX/macOS, the sudo wdutil info tool is extremely useful as it produces a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be utilized to generate a wide range of logs, although many of these are only relevant to wireless connectivity, similar to wdutil.
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will trigger a privacy warning. Running it without using the background option should open Finder in the correct location, or you can manually navigate to /var/tmp, or use the keyboard shortcut Cmd+Shift+G in Finder to access the path. Keep in mind that the file sizes are around 300MB, give or take.
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