How Can I DiagnOSe Wifi Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 205.175.75.123 or an IPv6 address like 2000:d8b:d8ce:5c0c:55ec:d367:3ccc:99b9. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not tech-savvy, conveying or even recognizing these addresses can be prone to errors and can quickly become complex. Moreover, this information does not provide any historical data, especially relating to past issues.
Navigating the World Wide Web
When trying to access a web page such as https://lind.biz, the first step is to consult a DNS server to transform the host portion (lind) along with the Top Level Domain (biz) of the URL into an IP address, like 47.7.38.113. In all web requests, your computer and browser actually transmit its type as well, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
Your default gateway is typically an automatically assigned address via DHCP. This gateway could be something like 192.168.238.74 (although they usually end in .1 or .254 based on the size of the scope) and this is where your computer forwards all its traffic to be routed further. For troubleshooting on Mac or Linux, you can refer to our detailed guide on how-to-fix-ipv6-connectivity/ or consult the following commands:
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 192.168.238.74 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 fe80:8af5:1fa0:bb83:f599%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): {33.153.218.91, 127.23.146.32}
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 2b:38:1d:80:8e:75
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 ed:d5:ba:55:04:18
}
Solutions for Connectivity Issues
Whether you are using a wired or wireless (Wi-Fi) medium to send data to your router, troubleshooting connectivity issues at the physical and data layer can be a complex task.
Steps to Resolve Connectivity Problems on Apple Devices
Regardless of the version of macOS you are running, whether it’s 10.15.4, 11.0.1, or 12.0.5, there are various tools available to help you troubleshoot connectivity issues. However, these tools may not provide a series of correlated values over time, making it difficult to track troubleshooting efforts. This is where automated remote troubleshooting becomes invaluable, especially for teams that operate in remote or Work From Anywhere (WFA) setups.
Useful Tools Embedded in macOS
One incredibly useful tool in macOS is sudo wdutil info, which provides a detailed dump of current wireless settings through the command-line interface. This tool can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive solution, generating a wide range of logs, although many of these logs may be point-in-time only in relation to wireless connectivity, similar to wdutil.
You can run sudo nohup /usr/bin/sysdiagnose -u & in the background, which will create logs in /var/tmp/<blah>.tar.gz. Alternatively, you can run sudo /usr/bin/sysdiagnose interactively, which will display a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which are typically around 300MB.
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