How To Troubleshoot Common Wifi Connectivity
Functioning of Internet Addressing
When connecting to the Internet, you will be assigned a Public IPv4 address such as 244.107.19.52 or an IPv6 address like 2000:1ce2:a72d:b943:5956:f5d9:bf39:20e5. You can verify this at https://test-ipv6.com/. However, conveying these addresses to individuals unfamiliar with technology, or even specifying MAC addresses like 12:d9:f9:6a:cc:7f, can be prone to errors and can become complex rapidly. Additionally, this does not provide any historical data, particularly when past issues occurred.
Navigating the Internet
In order to access a website such as https://abbott-abernathy.biz, you initially connect to a DNS server to convert the host portion (abbott-abernathy) combined with the Top Level Domain (biz) of the URL, to an IP address such as 135.173.148.236. Each of your computer and browser actually sends its type with all web requests for example Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).
Significance of Default Gateways
Your default gateway is generally an automatically configured address via DHCP. You are provided with a default gateway like 192.168.184.130 (though they usually end in .1 or .254 depending upon the scope size) and this is where your computer sends all its traffic to be routed onwards. For IPv6, an in-depth guide is available at how-to-fix-ipv6-connectivity/ but you can verify on Mac or Linux by:
### 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 192.168.184.130 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 fe80:1390:6c3d:4b65:87af%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): {146.40.58.248, 60.23.185.46}
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 12:d9:f9:6a:cc:7f
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 7d:a2:7d:a7:56:5b
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Take on Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.15.1, 11.5.7, or 12.0.1, there are a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a continuous set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams embracing remote work and the Work From Anywhere (WFA) culture.
Useful Built-in Tools
One useful tool on OSX/macOS is sudo wdutil info which provides a dump of current wireless settings to the CLI, and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool offers a more comprehensive option, generating a wide range of logs (although much of it is only point-in-time data in relation to wireless, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. For an interactive (though not very interactive) run, you can use sudo /usr/bin/sysdiagnose which will display a privacy warning. If 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 locate the path. However, be mindful of the file sizes, which are approximately 300MB.
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