How To Troubleshoot Common Wifi Router Issues
Understanding Internet Addressing
When using the Internet, it is common to have a Public IPv4 address, such as 80.127.186.167, or an IPv6 address, like 2000:5db8:2b39:3197:1a7b:da92:8720:41ca. These addresses can be verified on https://test-ipv6.com/. However, relaying these addresses, or even MAC addresses like c5:e6:85:51:d3:d5, to individuals who are not technologically inclined can be challenging and prone to errors. Moreover, this method does not retain historical data, particularly from previous incidents.
Navigating the World Wide Web
Accessing a website, such as https://abernathy.co, requires utilizing a DNS server to translate the host name (abernathy) and the Top Level Domain (co) of the URL into an IP address, such as 132.231.85.166. Additionally, your computer and browser provides its specifications with each web request, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
By default, your gateway is an address that is automatically configured through DHCP. Your computer is assigned a default gateway, like 10.99.171.106 (commonly ending in .1 or .254 based on the scope size), where all outgoing traffic is directed. For a detailed breakdown on IPv6, visit how-to-fix-ipv6-connectivity/, and for Mac or Linux, run the command:
command_here
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 10.99.171.106 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:fb16:e43b:dc99:fedb%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): {169.7.87.3, 68.148.132.19}
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 c5:e6:85:51:d3:d5
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 24:bd:9c:68:c5:6f
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS version 10.11.9, 11.1.5, or 12.0.2, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time, making it challenging to identify the root cause of issues. This is where automated remote troubleshooting becomes essential, especially for teams that adopt remote work and Work From Anywhere (WFA) arrangements.
Utilizing Built-in Scripts for Assistance
An extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting purposes. Moreover, the sysdiagnose tool offers a more comprehensive approach, generating a wide range of logs (although many are only related to wireless settings, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. For an interactive run, you can execute sudo /usr/bin/sysdiagnose, which will display a privacy warning. If not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which could be around 300MB or slightly more.
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