How To Fix Wifi Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 74.76.133.145 or an IPv6 address like 2000:9236:826e:7645:cb60:480:38c8:b552. Verifying this information is possible through https://test-ipv6.com/. However, for those who are not tech-savvy, conveying these addresses or referencing MAC addresses such as 9f:71:ac:40:99:a4 can be prone to errors and become complicated quickly. Moreover, this method does not provide any historical data, particularly when dealing with past issues.
Navigating the World Wide Web
In order to access a webpage like https://schaefer.net, your computer initially sends a request to a DNS server to convert the host portion (schaefer) combined with the Top Level Domain (net) of the URL into an IP address, such as 140.25.189.179. Every web request from your computer and browser includes its type, for example:
Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
Normally, your default gateway is an automatically configured address via DHCP, such as 192.168.39.246 (typically ending in .1 or .254, depending on the scope size). This is where your computer sends all its traffic to be routed onwards. For those using IPv6, there is a detailed guide on how-to-fix-ipv6-connectivity/ but it is possible to check on Mac or Linux with:
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 192.168.39.246 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:c95c:6461:ec4c:c789%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): {232.151.17.26, 104.255.50.50}
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 9f:71:ac:40:99:a4
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 e0:7c:33:c3:ae:d6
}
Solutions for Addressing Connectivity Issues with Wired and Wireless Networks
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Connectivity Problems on Apple macOS / OSX Devices
Irrespective of whether you are using OSX/macOS version 10.14.7, 11.4.6, or 12.1.7, there is a plethora of troubleshooting tools available. However, these manual interventions and scripts fail to provide a sequence of correlated values over a period of time. This is where automated remote troubleshooting proves to be highly beneficial, particularly for teams that have adopted remote work practices and embrace the concept of Work From Anywhere (WFA).
Leveraging In-Built Scripts for Assistance
A highly valuable tool on OSX/macOS is sudo wdutil info, which provides a detailed dump of the current wireless settings via the CLI, and it can also be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to produce a wide array of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & allows it to operate in the background and generate logs in the /var/tmp/<blah>.tar.gz directory. For an interactive (albeit minimal interaction) experience, you can executesudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not executed in the background, it should open Finder in the appropriate location, or users can navigate to /var/tmp or utilize Finder with Cmd+Shift+G to direct it to the specified path. However, users should be mindful of the file sizes which tend to be around 300MB or slightly more.
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