How Can I Fix Wifi Issues
Understanding How Internet Addressing Functions
When using the Internet, it’s common to have either a Public IPv4 address, such as 132.125.168.122, or an IPv6 address, like 2000:bbde:b28a:cf:1f65:4ae7:c41a:c1aa. This can be verified at https://test-ipv6.com/. However, explaining these addresses to non-technical individuals, or even mentioning MAC addresses, such as 21:b6:a6:db:7c:ab, can become quite complex and prone to errors. Furthermore, this method lacks historical data, especially in the case of past issues.
Navigating the World Wide Web
When attempting to access a website, such as https://davis.org, the initial step involves contacting a DNS server to convert the host part (davis) along with the Top Level Domain (org) of the URL into an IP address, such as 58.29.228.226. Each web request from your computer and browser includes its 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
Significance of Default Gateways
The default gateway is typically an address that’s automatically configured via DHCP. You’ll be assigned a default gateway, such as 192.168.155.69 (although they usually end in .1 or .254, depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, we have an in-depth guide on how-to-fix-ipv6-connectivity/, but you can check on Mac or Linux 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 192.168.155.69 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 fe80:50d7:bc8a:b757:5d9b%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): {117.234.149.186, 139.43.247.86}
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 21:b6:a6:db:7c:ab
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 5d:3e:78:ae:e4:f2
}
Solutions for Wired and Wireless Connectivity Issues
When it comes to sending 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
No matter which version of OSX/macOS you’re using, whether it’s 10.11.4, 11.6.9, or 12.1.6, there are various troubleshooting tools available. However, 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 embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool provides a CLI dump of current wireless settings and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a variety of logs, although many of them 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, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run, use sudo /usr/bin/sysdiagnose which will provide a privacy warning. The file sizes are approximately 300MB, so be cautious of that.
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