DiagnOSe Common Wifi Connectivity
Understanding the Basics of Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 or an IPv6 address. These addresses can be verified by visiting https://test-ipv6.com/. However, for those who are not familiar with technical jargon, communicating these addresses or MAC addresses can be challenging and prone to errors. Moreover, this method does not provide any historical data about past issues.
Navigating Through the World Wide Web
When trying to access a website, such as https://dubuque.info, you first need to access a DNS server to convert the host part (dubuque) and the Top Level Domain (info) of the URL into an IP address. Your computer and browser also send information about their types with every web request, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
The Significance of Automatic Gateways
Your default gateway is typically an automatically assigned address through DHCP. This default gateway, such as 192.0.0.234, serves as the point where your computer forwards all its traffic to be routed further. To troubleshoot IPv6 connectivity on Mac or Linux, a detailed tutorial is available at 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 192.0.0.234 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 fe80:24fd:7005:ca6e:7185%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): {254.44.130.111, 172.15.30.193}
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 5e:f2:0c:99:06:51
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 cb:07:70:52:b6:ef
}
Resolving Issues with Wired and Wireless Connections
When it comes to the physical and data layer, you may utilize a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting on Apple macOS / OSX
Regardless of which version of OSX/macOS you are currently using - whether it’s 10.14.1, 11.6.9, or 12.2.5, there are various tools available for addressing issues. Unfortunately, the manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting proves to be beneficial, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Embedded Scripts for Assistance
One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which produces a dump of current wireless settings in 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 relevant to wireless at a specific point in time, much like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will produce logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there isn’t much interaction), you can run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. However, be mindful of the file sizes, which are approximately 300MB.
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