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How Internet Addressing Solutions Work
When using the Internet, you are assigned a unique Public IPv4 address such as 37.20.237.249 or an IPv6 address like 2000:74c1:26:6b10:20ab:ae18:ba02:c2dc. You can verify this information by visiting https://test-ipv6.com/. However, conveying these addresses, or MAC addresses like 6f:2d:5f:f7:19:68, to individuals who are not tech-savvy can be prone to errors and can become complex very quickly. Furthermore, this method does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
In order to access a website like https://kautzer.info, your computer initially contacts a DNS server to convert the host portion (kautzer) along with the Top Level Domain (info) of the URL into an IP address, such as 85.255.198.38. Every time your computer and web browser sends a request to a website, it also sends its type, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.
Understanding the Significance of Default Gateways
Typically, your default gateway is an automatically assigned address via DHCP. You are given a default gateway like 172.30.58.47 (although they typically end in .1 or .254, depending on the scope size) and this is where all your computer’s traffic is directed for routing. To learn more about configuring IPv6, you can refer to our in-depth article on how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux, you can verify this information by using the following command:
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 172.30.58.47 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 fe80:997a:ac19:14a2:f1fa%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): {177.204.47.239, 41.197.122.167}
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 6f:2d:5f:f7:19:68
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 1d:b7:75:e1:2d:f1
}
Troubleshooting Options for Wired and Wireless Connections
When it comes to transmitting data to your router, there are options for using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Resolving Issues on Apple macOS / OSX Systems
Regardless of the version of OSX or macOS you’re using, whether it’s 10.11.3, 11.1.4, or 12.3.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes important, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless related settings 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 settings at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. For an interactive version, you can run sudo /usr/bin/sysdiagnose and it will provide a privacy warning. If 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 Finder to point to the path. However, be cautious of the file sizes, which are approximately 300MB.
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