How To Check Common Wifi Connectivity
Understanding Internet Addressing
When you’re on the Internet, you are assigned a unique address such as 227.164.187.3 for IPv4 or 2000:cafa:f51f:7956:d130:bb71:b6a5:503d for IPv6. This information can be verified at https://test-ipv6.com/. However, conveying these addresses, as well as MAC addresses like b0:cf:7e:54:cb:c6, to individuals who are not familiar with technology can be prone to errors and can become complex. Moreover, this method does not provide historical data, especially when previous issues occurred.
Navigating the World Wide Web
Accessing a website like https://kessler-marvin.co involves initially accessing a DNS server to convert the host portion (kessler-marvin) combined with the Top Level Domain (co) of the URL to an IP address such as 194.66.184.65. Furthermore, your computer and browser send information regarding their type with each web request, as exemplified by 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 automatically assigned address via DHCP. This address, for example 10.71.1.69 (commonly ending in .1 or .254 based on the scope size), is where your computer routes all of its traffic. For IPv6, a detailed explanation can be found here, and can be checked on Mac or Linux using the following command:
$ ip -6 route show
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 10.71.1.69 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 fe80:8b00:f373:f8fc:596f%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): {47.70.128.147, 36.170.27.193}
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 b0:cf:7e:54:cb:c6
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 ee:46:01:83:e9:c9
}
Solutions for Resolving Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, it’s essential to troubleshoot problems that may arise at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Strategies for Addressing Issues on Apple macOS / OSX
Regardless of whether you are running 10.14.5, 11.0.2, or 12.3.2, there are various tools available for troubleshooting on OSX/macOS. However, these manual actions and scripts do not provide a series of correlated values over time, which can be crucial for identifying and solving connectivity issues, particularly for remote work and Work From Anywhere (WFA) scenarios.
Utilizing Pre-Installed Scripts for Assistance
A valuable tool for troubleshooting wireless issues on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless settings. Additionally, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs, although many of these are only applicable to a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience, use the command sudo /usr/bin/sysdiagnose but be mindful of the large file sizes, reaching approximately 300MB.
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