How Can I Troubleshoot Wifi Connectivity
How the Addressing System of the Internet Functions
In the realm of the Internet, individuals can possess a Public IPv4 address such as 155.252.155.139 or an IPv6 address like 2000:f000:5364:15c9:b696:1b24:9b34:3288. Verification of this can be performed through https://test-ipv6.com/. However, for those who are not well-versed in technology, conveying these addresses, or even acknowledging MAC addresses like 5d:1e:c3:aa:05:1c, can be prone to errors and can become complex quite rapidly. Moreover, this does not provide any historical information (especially from previous occurrences of problems).
Navigating the Internet
When attempting to access a website such as https://mcclure.name, the initial step involves approaching a DNS server to convert the host portion (mcclure) in conjunction with the Top Level Domain (name) of the URL, to an IP address like 171.60.205.228. Upon making web requests, your computer and browser actually disclose their type e.g. Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured via DHCP. The default gateway appears as 192.0.0.49 (although they generally conclude with .1 or .254, contingent upon the size of the scope) and this is where your computer transmits all of its traffic to be further routed. For IPv6, an in-depth exploration is provided in how-to-fix-ipv6-connectivity/ but verification on Mac or Linux can be carried out by the following:
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 192.0.0.49 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:bee5:b1cc:45c9:5ae1%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): {73.153.221.50, 106.236.218.196}
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 5d:1e:c3:aa:05:1c
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 05:4a:48:ba:cb:40
}
Fixing Wired and Wireless Connection Issues
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 Strategies for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using, whether it’s 10.15.2, 11.6.9, or 12.2.3, there are multiple tools available for troubleshooting. However, manual actions and scripts do not provide a series of correlated values over time. This is where the importance of automated remote troubleshooting comes into play, especially for teams that are spending more time working remotely and embracing the concept of Work From Anywhere (WFA).
Effective Built-in Tools for Troubleshooting
One extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless related settings to the CLI 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 relevant to wireless settings, 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, which will trigger 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 usually around 300MB.
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