How To Support Common Wifi Connectivity
Functioning of Internet Addressing
When using the Internet, individuals may have a Public IPv4 address such as 165.113.46.180 or an IPv6 address like 2000:bae6:3df8:2090:d033:a859:34f5:56a7. It is possible to verify this by accessing https://test-ipv6.com/. However, trying to communicate these addresses, or even identifying MAC addresses like e9:be:91:27:27:02, can be fraught with errors for those who are not tech-savvy, and can become complicated quite quickly. Moreover, this method does not provide any historical information, especially when previous problems occurred.
Navigating the Internet
In order to reach a website such as https://spencer-kuvalis.net, the first step is to access a DNS server to convert the host portion (spencer-kuvalis) along with the Top Level Domain (net) of the URL, into an IP address like 153.248.121.148. All web requests sent by your computer and browser also contain its type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Significance of Default Gateways
The default gateway is usually an automatically assigned address via DHCP, often taking the form of 192.168.171.103 (although they typically end in .1 or .254 depending on the scope size). This is where your computer routes all of its traffic. For IPv6, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, this can be verified with the following code:
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 192.168.171.103 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:d092:c1fd:ded4:9723%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): {216.213.177.6, 134.53.41.78}
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 e9:be:91:27:27:02
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 89:12:83:27:27:8d
}
Resolving Issues with Wired or Wireless Connections
When it comes to sending data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you’re running, whether it’s 10.12.1, 11.4.5, or 12.3.7, there are various tools available for resolving issues. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes invaluable, especially for teams embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts
One particularly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the command line interface, and can also 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 point-in-time in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can 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, but be aware of the large file sizes of about 300MB.
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