How Do You Check Common Wifi Internet Issues
Understanding Internet Addressing
When it comes to the Internet, you may have a Public IPv4 address such as 44.93.44.100 or an IPv6 address like 2000:24eb:6025:2804:6015:a64e:acfb:8e42. It is possible to verify this information by visiting https://test-ipv6.com/. However, for individuals who are not technologically savvy, conveying these addresses, or even mentioning MAC addresses like a0:cb:86:9a:c5:5c, can become prone to error and quickly become complex. Furthermore, this does not provide any historical data, especially relevant to past issues.
Navigating the World Wide Web
To access a website such as https://denesik.info, the initial step involves accessing a DNS server to convert the host portion (denesik) combined with the Top Level Domain (info) of the URL into an IP address, such as 3.251.180.6. When making web requests, your computer and browser actually send their type, for example:
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address via DHCP. You obtain a default gateway like 192.168.164.124 (although they typically end in .1 or .254 depending on the scope size), and this is where your computer sends all of its traffic to be routed onward. For IPv6, there is an in-depth guide available on how-to-fix-ipv6-connectivity/, but it is possible to 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 192.168.164.124 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:be78:d0fd:811e:285e%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): {226.100.35.207, 158.89.85.160}
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 a0:cb:86:9a:c5:5c
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 db:3e:8c:c3:aa:ba
}
Troubleshooting Connectivity Issues: Wired vs Wireless
When it comes to sending data to your router, you’ll likely be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solving Problems on Apple macOS / OSX
No matter which version of OSX/macOS you’re using - whether it’s 10.11.6, 11.3.3, or 12.1.6 - 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 becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool is quite helpful as it provides a dump of the current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Another comprehensive tool is the sysdiagnose, which can generate a wide range of logs related to wireless, though many are only point-in-time logs just like 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 &. For an interactive run, use sudo /usr/bin/sysdiagnose with 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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