How Can I Understand Wifi Issues
Understanding Internet Addressing
When using the Internet, you will be assigned a Public IPv4 or an IPv6 address. For those without technical knowledge, communicating these addresses can be challenging, and even identifying MAC addresses poses challenges. The lack of historical data further complicates matters.
Navigating the World Wide Web
Accessing a web page begins with contacting a DNS server to translate the domain name and Top Level Domain of a URL into an IP address. Your computer and browser also provide information about the type of web requests being made.
The Significance of Default Gateways
Default gateways are typically automatically assigned addresses obtained through DHCP. These gateways serve as the destination for all outgoing traffic from your computer. Further information is available on setting up default gateways in IPv6 connectivity. Instructions for checking default gateways on Mac or Linux are also provided.
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 192.168.58.59 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:ac2d:d992:692f:5807%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): {35.57.235.21, 21.117.137.247}
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 3d:57:20:1e:c8:0b
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 d0:53:d4:8c:5d:c0
}
Wired vs Wireless Network Troubleshooting
When you are at the physical and data layer, you have the option to use a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.5, 11.6.2, or 12.0.5, 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 are embracing remote work and the Work From Anywhere (WFA) concept.
Useful Built-in Scripts
A very helpful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless related 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 are only point-in-time related to wireless, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, you can use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose and it will provide a privacy warning. When not run in the background, it should open Finder in the correct location. Just be aware of the file sizes, which are typically around 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
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