How Can I Support Common Wifi Issues
Understanding Internet Addressing
When using the Internet, you are assigned an IP address, such as 30.138.86.116 for IPv4 or 2000:e046:2ec3:4153:d1b7:2aab:a056:3169 for IPv6. To verify your IP address, you can use https://test-ipv6.com/. Communicating these addresses to those who are not technically inclined can be challenging, and even identifying MAC addresses, like 9e:27:34:c3:81:6b, can be error-prone and complex. Furthermore, this method does not provide any historical data, which is especially useful when troubleshooting past issues.
Navigating the World Wide Web
When attempting to visit a website, such as https://hegmann-schultz.net, your computer contacts a DNS server to convert the host portion (hegmann-schultz) and the Top Level Domain (net) of the URL into an IP address, like 85.109.190.91. Additionally, your computer and web browser include information about their type with every web request, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0.
The Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP. Your computer is provided with a default gateway, such as 172.26.76.65 (commonly ending in .1 or .254, depending on the scope size), to which it sends all traffic to be routed. For IPv6, detailed instructions can be found in the blog post how-to-fix-ipv6-connectivity/, and it can be verified on Mac or Linux using:
commands
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 172.26.76.65 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 fe80:9fd6:3b00:f99b:c255%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): {187.193.37.111, 84.24.224.27}
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 9e:27:34:c3:81:6b
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 46:a5:74:b0:2b:20
}
Resolving Problems with Wired and Wireless Connections
When it comes to the physical and data layer, you may be utilizing either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Solutions for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you have, whether it’s 10.13.6, 11.2.3, or 12.0.9, 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 embrace remote work and Work From Anywhere (WFA).
In-Built Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless-related settings to the CLI, and it can also be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose, which can generate a wide range of logs, although much of it is only related to wireless settings 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 &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, but be aware that it will give a privacy warning. The file sizes are approximately 300MB.
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