How Can I Check Wifi Internet Issues
How Addressing on the Internet Functions
When connecting to the internet, you might be assigned a Public IPv4 address such as 53.33.141.19 or an IPv6 address like 2000:c187:145c:7f5e:3acd:7637:29c5:b26b. These can be verified at https://test-ipv6.com/. Communicating these addresses, or even referring to MAC addresses like 67:e3:aa:ea:11:0b, can quickly become complex for those not well-versed in technology. Furthermore, this method does not provide any historical data (especially relating to past issues).
Navigating the World Wide Web
When trying to access a web page such as https://douglas.info, the first step is to contact a DNS server in order to translate the host portion (douglas) combined with the Top Level Domain (info) of the URL, into an IP address like 56.219.140.179. In every web request, your computer and browser sends its type, for example Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically assigned address through DHCP. It may look like 192.168.38.13 (though they usually end in .1 or .254 depending on the scope size), and this is the point to which your computer directs all its traffic to be routed onwards. For IPv6, a more detailed explanation can be found in how-to-fix-ipv6-connectivity/, while on Mac or Linux systems it can be checked as follows:
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 192.168.38.13 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 fe80:19ee:4026:c423:1316%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): {104.194.35.61, 216.1.250.138}
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 67:e3:aa:ea:11:0b
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 e0:b4:f8:54:4c:cd
}
Resolve Connectivity Issues for Wired or Wireless Networks
When it comes to transmitting data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS version 10.15.2, 11.1.2, or 12.1.4, there are various troubleshooting tools available. Unfortunately, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly 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 current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs (although much of it is point-in-time only in relation to wireless, similar to wdutil).
By running sudo nohup /usr/bin/sysdiagnose -u &, you can run it in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there is not much interaction), you can run 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 or use Finder with Cmd+Shift+G to point Finder to the path. Just be cautious of the file sizes, which are approximately 300MB more or less.
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