How To Understand Common Wifi Router Issues
The Function of Internet Addressing
When accessing the Internet, you may receive a Public IPv4 address such as 231.30.177.144 or an IPv6 address like 2000:4548:9595:e073:a3b6:2d1f:a697:bc2c. This information can be verified on https://test-ipv6.com/. However, for individuals who are not technically savvy, attempting to convey or recognize these addresses, or even reference MAC addresses like 19:ff:f9:42:c7:61, can be prone to errors and become complicated. Furthermore, this does not provide any historical data, especially regarding past issues.
Navigating the Internet
In order to access a webpage such as https://larson.co, you begin by accessing a DNS server to convert the host portion (larson) in combination with the Top Level Domain (co) of the URL into an IP address, for example, 61.163.46.186. Your computer and browser send their types with all web requests, for example, Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
Your default gateway is typically an automatically configured address through DHCP. A default gateway, such as 192.0.0.177 (although they usually end in .1 or .254 depending on the scope size), is where your computer sends all its traffic to be routed onwards. For IPv6, detailed instructions can be found on how-to-fix-ipv6-connectivity/ but it can also be checked on Mac or Linux 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 192.0.0.177 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 fe80:745f:86f:3c55:c365%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): {231.191.142.122, 62.27.88.85}
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 19:ff:f9:42:c7:61
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 b3:5e:48:d3:d0:9a
}
Diagnosing and Resolving Wired and Wireless Connectivity Issues
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.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you are using OSX or macOS 10.12.1, 11.1.3, or 12.3.2, there are various tools available for troubleshooting. However, manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that adopt remote work and Work From Anywhere (WFA) practices.
Useful Built-in Scripts
An important tool for troubleshooting on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI. This tool can also be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a wide range of logs related to wireless issues, although much of it is only point-in-time data, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose and it will give 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 Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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