How Do You DiagnOSe Wifi Issues
Understanding IP Addresses
When using the Internet, you are assigned an IP address such as 50.95.114.155 (IPv4) or 2000:2273:5f4e:3337:536e:9699:88a1:d4e5 (IPv6). These can be verified on https://test-ipv6.com/. However, conveying and managing these addresses, as well as MAC addresses like d9:6c:0b:e0:1a:df, can be error-prone and complex for non-technical users. This method also lacks historical data, especially relating to previous issues.
Navigating the Internet
When accessing a website such as https://stark.name, the initial step involves using a DNS server to convert the URL’s host portion (stark) along with the Top Level Domain (name) to an IP address like 83.46.147.43. Additionally, your computer and browser both provide their type with each web request, 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
The Significance of Default Gateways
The default gateway is typically automatically configured via DHCP and is usually an address ending in .1 or .254, depending on the scope size, such as 172.26.169.168. This is where your computer directs all traffic for routing. For IPv6, a more detailed explanation is available at how-to-fix-ipv6-connectivity/ and can be verified on Mac or Linux 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 172.26.169.168 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:dfb5:7c5a:c9f:4a26%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): {22.44.28.9, 180.222.229.177}
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 d9:6c:0b:e0:1a:df
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 a2:7a:ab:b5:0b:83
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data, whether through a wired or wireless (Wi-Fi) medium, it is important to troubleshoot any issues that may arise at the physical and data layer, especially when dealing with your router.
Addressing Problems on Apple macOS / OSX Systems
No matter which version of OSX/macOS you are using, whether it’s 10.15.7, 11.3.6, or 12.2.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that have embraced remote work and Work From Anywhere (WFA) arrangements.
Utilizing Pre-Installed Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can 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.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background, writing logs to /var/tmp/<blah>.tar.gz. For an interactive run (although there is minimal interaction), you can use sudo /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 using Finder with the Cmd+Shift+G command. Be mindful of the file sizes, which typically range around 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
