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Understanding the Mechanism of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 199.246.95.92, or an IPv6 address, such as 2000:b964:13d2:1da4:afc5:cf8e:f8b8:f700. You can verify this information by visiting https://test-ipv6.com/. However, attempting to communicate these addresses to those who are not technically inclined, or even mentioning MAC addresses like 9e:96:85:b7:30:5e, can be prone to errors and become complex quite rapidly. Furthermore, this method does not provide any historical data, especially regarding previous issues.
Navigating the Internet
In order to access a website like https://champlin-beahan.net, your device first contacts a DNS server to convert the combined host portion (champlin-beahan) and the Top Level Domain (net) of the URL into an IP address, such as 188.202.87.112. Your computer and browser actually sends its type with all web requests, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is normally an address that is automatically configured via DHCP. You receive a default gateway, such as 10.101.207.112 (though they typically end in .1 or .254 depending on the scope size), and this is where your computer forwards all of its traffic to be routed. For IPv6, we offer an in-depth analysis on how-to-fix-ipv6-connectivity/, but you can verify this 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 10.101.207.112 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:c4b2:57cb:c47e:bef5%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): {153.136.141.227, 139.66.214.74}
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 9e:96:85:b7:30:5e
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 b9:13:f4:31:2f:bd
}
Resolving Issues with Wired and Wireless Connections
When transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX
Irrespective of your OSX/macOS version - whether it’s 10.14.5, 11.4.9, or 12.3.3, there are various troubleshooting tools available. However, these tools only provide individual data and not a series of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams practicing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
In OSX/macOS, the sudo wdutil info tool is extremely beneficial as it provides a dump of the current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Moreover, the sysdiagnose tool can be used to generate a wide range of logs, although most of the data is only relevant to a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will result in a privacy warning. When not run in the background, it will open Finder in the correct location, allowing you to navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the specific path. However, be cautious of the file sizes, which are approximately 300MB.
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