How To Check Wifi Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 59.179.61.132 or an IPv6 address like 2000:6fa2:3ba7:e929:3b1b:3af8:3d56:cd35. These addresses can be verified using https://test-ipv6.com/. However, understanding and communicating these addresses, as well as MAC addresses like 3f:15:f5:d9:38:74, can be challenging for those without technical knowledge. Furthermore, this method does not provide any historical data, especially related to past issues.
Navigating the World Wide Web
When accessing a web page such as https://jones.co, you first connect to a DNS server in order to convert the host part (jones) along with the Top Level Domain (co) of the URL to an IP address, like 6.45.73.146. Your computer and browser includes these details in all web requests, for example:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateway Configuration
The default gateway is typically assigned automatically through DHCP and will be a default gateway like 192.0.0.117 (often ending in .1 or .254 depending on the size of the network). This is the point where your computer sends all of its traffic to be routed further. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/ or you can perform a check on a Mac or Linux system using the following method:
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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 192.0.0.117 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:aa8a:8473:741c:4d8c%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): {150.249.60.108, 0.1.188.41}
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 3f:15:f5:d9:38:74
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 df:8c:6a:39:93:2e
}
Fixing Connection Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using either 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 10.12.4, 11.0.4, or 12.3.9 - there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time, which is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts
One convenient tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI 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 at a specific point in time, similar to wdutil.
To run it in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience, run sudo /usr/bin/sysdiagnose and be aware of the large file sizes of approximately 300MB. When not run in the background, it should open Finder in the correct location or you can navigate to /var/tmp using Finder or by using Cmd+Shift+G to point Finder to the path.
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