DiagnOSe Wifi No Access
The Functionality of Internet Protocol Addressing
When using the Internet, one can have a Public IPv4 address, such as 234.0.228.61, or an IPv6 address, like 2000:fd4f:c2eb:358f:65f2:5455:2878:41c7. These can be verified at https://test-ipv6.com/. However, presenting these addresses, or MAC addresses like d3:63:3c:7c:cc:b8 to those without technical expertise can be prone to errors and become complex. Moreover, this fails to provide any historical data, particularly from past issues.
Navigating the Internet
To access a webpage such as https://hane-considine.net, you first reach out to a DNS server to convert the host part (hane-considine) combined with the Top Level Domain (net) of the URL into an IP address, like 255.98.215.180. Your computer and browser indicate their type with all web requests, such as: 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 Predetermined Gateways
Commonly, your default gateway is an automatically configured address via DHCP. Usually ending in .1 or .254 depending upon the scope size, you receive a default gateway, such as 192.168.97.76, and this is where your computer forwards all its traffic for routing. For IPv6, we offer an in-depth analysis on how-to-fix-ipv6-connectivity/, but you can verify 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 192.168.97.76 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 fe80:5a24:d302:840b:af7c%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): {139.17.89.156, 216.164.230.122}
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 d3:63:3c:7c:cc:b8
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 a3:df:ed:fa:eb:8c
}
Solutions for Troubleshooting Wired and Wireless Networks
When it comes to sending data at the physical and data layer, you have the option of using either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Tips for Handling Issues on Apple macOS / OSX Devices
Regardless of the version of OSX/macOS you are using, whether it’s 10.13.3, 11.1.1, or 12.0.2, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set 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).
Useful Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (though there isn’t much interaction), you can run sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp manually, or use Finder with Cmd+Shift+G to navigate to the path. Just be aware that the file sizes are around 300MB, more or less.
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