Test Mac Internet Connection
The Functionality of Internet Addressing
When it comes to the Internet, individuals are assigned unique identifiers in the form of Public IPv4 or IPv6 addresses. For example, 185.128.154.192 or 2000:60f7:79aa:27c6:3a37:c6cf:28d2:b2a4. These can be verified at https://test-ipv6.com/. However, conveying these addresses and even MAC addresses like 73:a7:fa:f5:81:ae to those who are not well-versed in technology can be prone to error and can quickly become complex. Moreover, this method does not provide any historical data, particularly during past issues.
Navigating the Online Domain
Accessing a website such as https://haley.org involves an initial interaction with a DNS server, which converts the host portion (haley) in combination with the Top Level Domain (org) of the URL to an IP address like 6.133.212.44. Every web request from your computer and browser also includes specific information, for instance, Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Understanding the Significance of Default Gateways
The default gateway, usually an automatically assigned address via DHCP, serves as the designated route for all outbound traffic from your computer to follow. For instance, you may receive a default gateway like 172.18.170.201 (often ending in .1 or .254 based on the size of the scope). More detailed guidelines on configuring default gateways for IPv6 can be found at how-to-fix-ipv6-connectivity/. You can also verify this process on Mac or Linux using:
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 172.18.170.201 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:a988:aa85:cf70:e0d3%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): {20.142.83.205, 176.152.216.185}
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 73:a7:fa:f5:81:ae
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 5d:77:79:44:9d:f1
}
Resolving Issues with Wired and Wireless Connections
When transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Problems on Apple macOS / OSX
Irrespective of the version of OSX/macOS you are using, whether it’s 10.13.1, 11.2.3, or 12.0.5, there are various tools available for dealing with troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, particularly for teams that are inclined towards remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A highly 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 also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although many are 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 (even though there isn’t much interaction), you can use the command sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. If 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 direct Finder to the path. However, be cautious of the file sizes, which are approximately 300MB.
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