How Can I Troubleshoot Wifi Issues
Understanding the Functioning of Internet Addressing
When using the Internet, you are assigned a unique Public IPv4 address such as 16.213.52.74 or an IPv6 address like 2000:10e6:20b8:3389:39a1:b322:9bc6:e22d. You can verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to individuals who are not technologically savvy, or even discussing MAC addresses like 49:a6:ec:cf:39:8f, can be prone to errors and become complex quickly. Moreover, this process does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When attempting to access a website such as https://bruen-schaden.biz, your computer initially contacts a DNS server to convert the host portion (bruen-schaden) combined with the Top Level Domain (biz) of the URL into an IP address such as 98.135.202.243. Furthermore, your computer and browser send their information type with every web request, for instance, Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
The Significance of Standard Gateways
By default, your gateway is usually an address that is automatically configured via DHCP. Typically, you receive a default gateway like 192.168.16.91 (though they generally end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, a comprehensive analysis can be found at how-to-fix-ipv6-connectivity/, although you can verify this on Mac or Linux by using the following command:
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 192.168.16.91 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 fe80:6bbd:87d4:5352:f39a%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): {125.29.26.0, 62.176.202.109}
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 49:a6:ec:cf:39:8f
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 76:fa:91:9c:08:62
}
Resolving Connectivity Issues in Wired and Wireless Networks
When it comes to transferring data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you’re running OSX/macOS 10.14.7, 11.0.9, or 12.1.2, there are various troubleshooting tools available. However, the manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is sudo wdutil info, which provides a CLI dump of current wireless settings 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 settings at a specific point in time, similar to wdutil.
Runningsudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can usesudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp with Cmd+Shift+G in Finder. Keep in mind that the file sizes are typically around 300MB.
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