How Can I Support Common Wifi No Access
Understanding the Function of IP Addresses
When accessing the Internet, you are assigned a unique IP address, such as 79.50.91.222 for IPv4 or 2000:cdf0:eff1:8190:9f0f:7abc:987e:be for IPv6. Verifying these addresses is possible by visiting https://test-ipv6.com/. However, communicating these addresses to those who are not well-versed in technology, or referencing MAC addresses like 1d:4b:bc:78:fb:cb, can be prone to errors and become convoluted. Furthermore, this method does not provide historical data, especially when addressing previous problems.
Navigating to Websites
To reach a website like https://hahn.com, the first step involves accessing a DNS server to translate the host portion (hahn) combined with the Top Level Domain (com) of the URL into an IP address, such as 160.243.198.113. Every web request from your computer and browser includes its type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Automatic Gateways
Your default gateway is typically an address that is automatically configured through DHCP. It is likely that you receive a default gateway like 172.16.93.10 (commonly ending in .1 or .254 depending on the scope size), which is where your computer directs all of its traffic to be routed onwards. For IPv6, detailed instructions for Mac or Linux can be found in the article how-to-fix-ipv6-connectivity/.
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 172.16.93.10 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:b8af:4f59:18b3:4157%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): {73.16.153.34, 10.73.234.114}
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 1d:4b:bc:78:fb:cb
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 1c:4f:13:ac:4f:d5
}
Resolving Connectivity Issues: Wired vs. Wireless
When it comes to transmitting data to your router, you may be using a medium that is either wired or wireless (Wi-Fi) at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of which version of OSX/macOS you are using, whether it’s 10.12.5, 11.6.1, or 12.2.4, there are various tools available for solving connectivity issues. However, these tools do not provide a series of correlated values over time, which is essential for remote troubleshooting, especially for teams involved in remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool for OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is 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 (but minimal interaction) experience, run the command sudo /usr/bin/sysdiagnose, which will give a privacy warning. If not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are around 300MB.
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