How Do You Troubleshoot Common Wifi Router Issues
Understanding Internet Addressing
When using the Internet, it is common to receive a Public IPv4 address such as 194.19.157.96 or an IPv6 address like 2000:ea8:6bea:4a4c:3b11:c7d:bef:ba57. This information can be verified through https://test-ipv6.com/. However, conveying these addresses to individuals who are not tech-savvy, or even mentioning MAC addresses like 65:b7:79:d2:bf:b6, can be prone to errors and quickly becomes complex. Moreover, it does not provide any historical data, particularly when problems occurred in the past.
Navigating the World Wide Web
When accessing a website such as https://gleichner.info, the first step involves accessing a DNS server to convert the host portion (gleichner) combined with the Top Level Domain (info) of the URL into an IP address like 142.25.84.59. Every web request from your computer and browser includes its type, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address obtained through DHCP. An example of a default gateway is 192.168.65.68, although they usually end in .1 or .254 based on the scope size. This is the point where your computer directs all its traffic to be routed further. Further information on IPv6 can be found in our in-depth guide on how-to-fix-ipv6-connectivity/. If using Mac or Linux, the default gateway can be verified with:
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 192.168.65.68 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:bdc1:4caf:64cc:5454%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): {5.47.117.140, 18.40.7.188}
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 65:b7:79:d2:bf:b6
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 45:de:95:60:97:57
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using, whether it’s 10.14.5, 11.4.7, or 12.3.2, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Embedded Scripts for Assistance
A highly useful tool on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to create a wide range of logs, although much of it is only point-in-time in relation to wireless, similar to wdutil.
To run it in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose and it will issue a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Cmd+Shift+G. Keep in mind that the file sizes are around 300MB.
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