DiagnOSe Wifi Connectivity

The Functioning of Internet Addressing

When using the Internet, you will be assigned a Public IPv4 address, such as 208.195.212.167, or an IPv6 address, such as 2000:a044:1fd8:2306:5fda:4a6a:efe5:d562. This can be verified at https://test-ipv6.com/. However, for those unfamiliar with technology, trying to communicate these addresses, or even mention MAC addresses like 96:a5:4f:97:9e:ef, can be prone to error and quickly become complicated. Moreover, this does not provide any historical data, especially when dealing with past issues.

How to Reach Websites

In order to access a website like https://kautzer.co, you first need to connect to a DNS server to convert the host portion (kautzer) combined with the Top Level Domain (co) of the URL into an IP address, such as 250.196.231.171. Your computer and browser actually include its type in all web requests, for instance:
Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16

The Significance of Default Gateways

The default gateway is typically an automatically allocated address via DHCP. You will receive a default gateway like 10.186.255.45 (although they usually end in .1 or .254 depending on the scope size) and this is where your computer sends all its traffic to be routed onwards. For IPv6, there is a detailed explanation available in how-to-fix-ipv6-connectivity/ but you can check 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  10.186.255.45    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   fe80:783c:789e:95a9:7d38%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): {199.97.150.242, 59.115.56.61}
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 96:a5:4f:97:9e:ef
  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 e9:86:96:a7:aa:7b
}

Resolve Connectivity Issues for Wired and Wireless Networks

When it comes to sending data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.

Troubleshooting on Apple macOS / OSX

Regardless of the version of OSX/macOS you are operating on, whether it’s 10.15.9, 11.5.5, or 12.0.8, there is a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and Work From Anywhere (WFA).

Utilizing Built-in Scripts for Assistance

One of the useful tools on OSX/macOS is “sudo wdutil info”, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the “sysdiagnose” tool can be utilized to generate a wide range of logs, although much of it is only relevant to the wireless issue, similar to wdutil.

Running “sudo nohup /usr/bin/sysdiagnose -u &” in the background will write logs to “/var/tmp/.tar.gz”. For interactive use, you can simply 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” using Finder with Cmd+Shift+G or use the path. Keep in mind that the file sizes are approximately 300MB.

Possibly Helpful Videos

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Table 1.0 - Video Help