Fix Common Wifi Router Issues
Understanding Internet Addressing
When using the Internet, you will receive either a Public IPv4 address like 203.3.30.205 or an IPv6 address like 2000:4026:f20:783b:332f:d82b:cf02:4b8f. You can verify these addresses using this link. However, attempting to convey these addresses to non-technical individuals, or even discussing MAC addresses like b1:26:5d:b5:a5:88, can easily lead to errors and confusion. Moreover, this approach does not provide any historical data to address previous issues.
Navigating the World Wide Web
To access a webpage, such as https://schmidt-ritchie.com, you first consult a DNS server to convert the host portion (schmidt-ritchie) and the Top Level Domain (com) of the URL into an IP address, such as 217.126.164.68. Your computer and browser include information about their type in every web request, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
Your default gateway is typically an automatically assigned address through DHCP. For instance, you might receive a default gateway like 192.168.146.33 (often ending in .1 or .254 based on the scope size), and this is where your computer sends all its outbound traffic to be routed. For IPv6, a detailed explanation can be found in this guide, while on Mac or Linux, you can verify this by 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 192.168.146.33 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:a670:6939:f78a:819d%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): {51.242.26.193, 7.227.125.15}
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 b1:26:5d:b5:a5:88
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 ea:f5:78:fc:0f:7d
}
Solutions for Resolving Wired and Wireless Issues
When dealing with data transmission at the physical and data layer, it is common to use either a wired or wireless (Wi-Fi) medium to send the data to your router.
Steps to Take on Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.12.2, 11.1.1, or 12.1.6, 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 invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI, and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are only point-in-time related to wireless, like the wdutil tool.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use sudo /usr/bin/sysdiagnose, but keep in mind that 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. Be aware that the file sizes are approximately 300MB.
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