DiagnOSe Wifi Internet Issues
Understanding the Function of Internet Addressing
When using the Internet, individuals are assigned Public IPv4 addresses, such as 159.255.103.20, or IPv6 addresses, like 2000:e97d:f604:8355:28a3:d357:78b5:887f. It is possible to verify these addresses through https://test-ipv6.com/. However, explaining or communicating these addresses to non-technical individuals, and even mentioning MAC addresses such as 7f:b3:07:b3:13:fb, can quickly become complicated and prone to errors. Furthermore, this approach does not provide any historical data, particularly relating to past issues.
Navigating the World Wide Web
When attempting to access a website, like https://oberbrunner.co, users start by connecting to a DNS server to translate the URL’s host portion (oberbrunner) and its Top Level Domain (co) into an IP address, such as 171.230.118.173. Additionally, users' computers and browsers transmit their type with each web request, for example:
Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Recognizing the Significance of Default Gateways
Typically, a default gateway is automatically configured through DHCP. This results in obtaining a default gateway address, such as 192.0.0.183 (although they often end in .1 or .254 based on the scope size), where users' computers forward all their traffic for routing. For IPv6, a thorough explanation is available at how-to-fix-ipv6-connectivity/, and users can verify this on Mac or Linux by using the following commands:
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 192.0.0.183 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 fe80:85c5:4740:b695:1ecc%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): {101.59.73.219, 177.2.188.23}
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 7f:b3:07:b3:13:fb
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 3d:f0:93:0d:da:6a
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps for Apple macOS / OSX Troubleshooting
No matter which version of OSX/macOS you are using, such as 10.15.6, 11.0.6, or 12.1.6, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Recommended Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless-related settings to the CLI and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is related to wireless as with wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there is not much interaction), you can run sudo /usr/bin/sysdiagnose and it will provide a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. Just be cautious of the file sizes, which are approximately 300MB.
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