How Can I Troubleshoot Wifi Router Issues
Understanding Internet Protocol Addressing
The way the Internet works involves having a Public IPv4 address, such as 139.71.136.174 or an IPv6 address like 2000:2eff:61d1:cf36:acbd:4266:c7be:d290. We can verify this by visiting https://test-ipv6.com/. However, explaining these addresses, or even calling out MAC addresses like ca:06:d1:96:c0:5d, can be challenging for non-technical users. Furthermore, it does not provide any historical data.
The Process of Connecting to Websites
When accessing a website like https://tillman.co, you begin by reaching out to a DNS server to convert the host portion (tillman) in combination with the Top Level Domain (co) of the URL into an IP address, such as 72.71.121.52. Your computer and browser both send their type with all web requests, for instance: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically assigned address via DHCP. For example, you might receive a default gateway like 192.0.0.243, although they often end in .1 or .254 depending on the scope size. This is the point where your computer directs all its traffic to be routed onwards. For IPv6, there is an in-depth explanation available on how-to-fix-ipv6-connectivity/, but you can check 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 192.0.0.243 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:ac49:1057:ea4e:ea94%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): {37.146.160.215, 72.179.70.138}
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 ca:06:d1:96:c0:5d
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 ef:bd:36:91:55:b8
}
Resolving 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) connection at the physical and data layer.
Actions to Take for Apple macOS / OSX Users
Whether you are using OSX/macOS versions such as 10.14.2, 11.6.9, or 12.2.5, there are a variety of troubleshooting tools available. However, these manual interventions and scripts do not provide a continuous set of related data points over time. This is where automated remote troubleshooting becomes crucial, especially for teams that have adopted remote work and embrace the concept of Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a comprehensive dump of current wireless settings to the CLI, and it can also be configured to generate specific logs for troubleshooting purposes. Moreover, the sysdiagnose tool can be used to generate a wide range of logs, although much of the information is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running the command sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and save logs in the /var/tmp/<blah>.tar.gz directory. If you prefer to run it interactively (although there is minimal interaction), you can execute the command sudo /usr/bin/sysdiagnose which will prompt a privacy warning. When not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder or use Cmd+Shift+G in Finder to direct it to the specific path. However, keep in mind that the file sizes are approximately 300MB or slightly more.
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