How Can I Troubleshoot Wifi Internet Issues
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a Public IPv4 address such as 67.16.35.137 or an IPv6 address like 2000:b605:d219:b1f1:6918:a4f:2259:ea7d. This information can be verified at https://test-ipv6.com/. However, relaying or discussing these addresses, as well as MAC addresses like 0f:ec:fa:ab:71:4e, can be error-prone for individuals who are not tech-savvy and can become complicated. Moreover, this method does not provide any historical data, particularly during previous incidents.
Navigating the World Wide Web
In order to access a webpage such as https://jacobson.net, you must first contact a DNS server to convert the host portion (jacobson) combined with the Top Level Domain (net) of the URL into an IP address, such as 111.253.32.176. Your computer and browser also transmit their type with every web request, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
Your default gateway is typically an address configured automatically via DHCP. This gateway address, such as 192.168.231.246 (usually ending in .1 or .254 depending on the scope size), is where your computer forwards all its traffic. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/, but you can also verify on Mac or Linux using:
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 192.168.231.246 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 fe80:55d1:3252:6678:d71b%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): {214.247.127.197, 71.55.92.39}
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 0f:ec:fa:ab:71:4e
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 b5:8d:fc:53:dc:82
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Options for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.15.7, 11.0.8, or 12.1.5, there are various tools available for resolving issues. However, these manual actions and scripts do not provide a series of correlated values over time. Therefore, automated remote troubleshooting can be particularly useful, especially for teams that are working remotely and embracing Work From Anywhere (WFA).
Utilizing Built-in Scripts
On OSX/macOS, the sudo wdutil info tool is quite useful as it provides a dump of the current wireless-related 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 pertains to wireless settings and is only point-in-time, 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, use the command sudo /usr/bin/sysdiagnose (although there is not much interaction). Just be aware that the file sizes are around 300MB.
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