How Do You Understand Wifi Router Issues
Understanding Internet Addressing
When using the Internet, you are assigned a public IPv4 or IPv6 address. These addresses can be checked using tools like https://test-ipv6.com/. However, communicating these addresses and MAC addresses to non-technical individuals can be challenging and prone to errors, especially when needing historical data.
Navigating the Internet
Accessing a website involves translating the URL to an IP address through a DNS server. Additionally, web requests include information about the computer and browser type. For example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
The Significance of Default Gateway
The default gateway, usually obtained through DHCP, is where all traffic is routed onwards. Default gateways typically end with .1 or .254, depending on the scope size. For IPv6, troubleshooting steps can be found at how-to-fix-ipv6-connectivity/, and can be checked on Mac or Linux systems.
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 172.20.151.252 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 fe80:23b5:4dae:9566:25fa%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): {171.97.104.146, 185.155.244.193}
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 90:11:09:68:c2:91
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 69:fe:3a:4f:61:b0
}
Solve Problems with Wired and Wireless Networks
When it comes to transferring 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
Regardless of the version of OSX/macOS you are using, whether it’s 10.15.1, 11.5.6, or 12.1.9, 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 valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilize the Following Built-in Scripts
An extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless related settings to the command line interface (CLI). This command can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings, similar to what wdutil provides.
To run the sysdiagnose tool in the background and generate logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will open Finder in the correct location or allow you to navigate to /var/tmp. Keep in mind that the file sizes are approximately 300MB.
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