How To Check Common Wifi Issues
Understanding Internet Addressing
When using the Internet, you will be assigned a Public IPv4 address such as 157.24.188.171 or an IPv6 address like 2000:50aa:cc45:92d4:2e6:1782:ce50:6a70. These addresses can be verified using https://test-ipv6.com/. However, it can be difficult for non-technical individuals to communicate these addresses, and also MAC addresses like 17:5c:34:05:d9:5a, without making errors. Furthermore, this method does not provide any historical data, especially during previous issues.
Navigating the World Wide Web
When attempting to access a website such as https://purdy.biz, the first step is to connect to a DNS server that translates the host portion (purdy) along with the Top Level Domain (biz) of the URL into an IP address, like 212.250.201.102. When making web requests, your computer and browser also send their types, e.g. Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of the Default Gateway
The default gateway is typically an automatically configured address obtained via DHCP. It is similar to a default gateway, such as 172.30.222.101 (usually ending in .1 or .254 depending on the scope size), to which your computer sends all of its traffic to be routed onwards. For IPv6, detailed information can be found at how-to-fix-ipv6-connectivity/, but it can be checked on Mac or Linux 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 172.30.222.101 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 fe80:510a:2b13:95b3:344b%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): {143.123.194.93, 242.51.2.117}
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 17:5c:34:05:d9:5a
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 19:b4:11:71:16:47
}
Fixing Connectivity Issues in Wired and Wireless Networks
When it comes to transmitting data to your router, you can either use a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you’re running, whether it’s 10.13.1, 11.0.1, or 12.2.5, there are various troubleshooting tools available. However, these manual actions and scripts don’t provide a series of correlated values over time, which is crucial for effective troubleshooting. This is where automated remote troubleshooting becomes beneficial, especially for teams that are engaged in remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool is extremely helpful as it provides a dump of the current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool offers a more comprehensive solution, generating a wide range of logs (though many are only point-in-time related to wireless, similar to wdutil).
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively with the command sudo /usr/bin/sysdiagnose, which will provide a privacy warning. If 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. Just be mindful of the file sizes, which are usually around 300MB.
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