Understand Common Wifi Internet Issues
Understanding Internet Address Allocation
When using the internet, an individual may be assigned a Public IPv4 address such as 229.87.10.129 or an IPv6 address like 2000:c1cc:fdb0:b48e:5a7b:7d1e:7c6b:115e. The process of conveying these addresses to non-technical users or even referencing MAC addresses like f9:cb:e8:50:1e:b0 can be cumbersome and error-prone. Moreover, this method fails to provide any historical information about past issues.
Navigating the World Wide Web
When attempting to visit a webpage, such as https://witting.io, you begin by accessing a DNS server to translate the combination of the host portion (witting) and the Top Level Domain (io) of the URL into an IP address, like 221.225.34.71. With each web request, your computer and browser also transmit their type, for example, Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateways
The default gateway is typically an address automatically configured via DHCP. It may be something like 172.29.88.53 (often ending in .1 or .254 based on the scope size), and is the point to which your computer directs all outgoing traffic to be routed further. For more information on IPv6, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/. Alternatively, you can validate this 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 172.29.88.53 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 fe80:3246:a8db:2750:b5e1%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): {148.66.23.238, 59.56.148.84}
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 f9:cb:e8:50:1e:b0
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 73:81:35:5d:a2:65
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX Systems
No matter which version of OSX/macOS you are currently running, whether it’s 10.13.5, 11.1.8, or 12.1.8, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
In-Built Tools for Assistance
An essential tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings in the command line, 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 at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will run it in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose, which will give 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. However, be mindful of the file sizes, which are approximately 300MB.
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