How To Troubleshoot Wifi Router Issues
Understanding How Internet Addresses Function
When connecting to the Internet, it is common to receive a Public IPv4 address, such as 24.120.231.228, or an IPv6 address, such as 2000:34c0:c5ec:7895:2f95:a199:866c:ef62. This can be verified at https://test-ipv6.com/. However, for individuals who are not well-versed in technology, attempting to relay and manage these addresses, including MAC addresses like 92:37:8a:50:11:89, can be prone to errors and become complex rather quickly. Furthermore, this does not provide any historical data, particularly during previous incidents.
Navigating the Internet
Accessing a webpage, such as https://hand-waters.org, initially requires reaching out to a DNS server to convert the host portion (hand-waters) combined with the Top Level Domain (org) of the URL into an IP address, such as 24.255.110.199. Interestingly, your computer and browser disclose their types with every web request, for instance: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Typically, your default gateway is automatically configured through DHCP, resulting in a default gateway like 172.24.136.30 (although they generally end in .1 or .254 based on the scope size). This is where your computer redirects all its traffic for further routing. For IPv6, we have provided an in-depth analysis on how-to-fix-ipv6-connectivity/, but you can also verify on Mac or Linux using:
### 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 172.24.136.30 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 fe80:9e3c:24:a7e7:9255%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): {5.83.106.199, 21.10.116.13}
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 92:37:8a:50:11:89
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 b2:2a:01:09:45:32
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to the physical and data layer, you might be utilizing either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting Guide for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are running - whether it’s 10.14.5, 11.6.9, or 12.1.5 - 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 essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs related to wireless issues, although much of it is only point-in-time data similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will display a privacy warning. When 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 point Finder to the path. Be mindful of the file sizes, which are roughly around 300MB.
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