How To Support Common Wifi Issues
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a unique Public IPv4 address such as 81.54.215.218 or an IPv6 address like 2000:709b:626d:3285:1ec4:40c2:c685:4c9f. To verify your assigned address, you can visit https://test-ipv6.com/. However, attempting to convey these addresses to individuals who are not familiar with technology, or even mentioning MAC addresses like da:d2:ee:62:06:e1, can be prone to errors and can become complicated very quickly. It also does not provide any historical data, especially when dealing with past issues.
Navigating the World Wide Web
When accessing a webpage such as https://bauch-schinner.name, your request is initially routed to a DNS server to translate the host part (bauch-schinner) combined with the Top Level Domain (name) of the URL to an IP address such as 183.117.222.7. Interestingly, your computer and browser sends its type with all web requests, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
The Significance of Default Gateways
Your default gateway is typically an address that is auto-configured via DHCP. This default gateway, which may end in .1 or .254 based on the scope size, such as 10.113.152.6, is where your computer sends all its traffic to be routed onwards. For IPv6, you can find more detailed information on how-to-fix-ipv6-connectivity/. On Mac or Linux, the default gateway can be checked 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 10.113.152.6 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 fe80:878d:bc87:33a1:d83b%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): {113.91.67.221, 25.205.101.27}
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 da:d2:ee:62:06:e1
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 99:1a:f7:5c:a4:f6
}
Resolve Issues with Wired or Wireless Connections
When transmitting data, you may utilize either a wired or wireless (Wi-Fi) medium to communicate with your router at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you are using, whether it’s 10.14.5, 11.1.7, or 12.2.8, there are various tools available for resolving issues. However, these manual actions and scripts do not provide a continuous set of correlated values over a period of time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose tool, which can generate a wide range of logs, although many of them are only relevant to a specific point in time in relation to wireless, similar to wdutil.
To run it 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 sudo /usr/bin/sysdiagnose, but beware of the large file sizes of about 300MB or more.
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