How Can I Understand Mac Internet
Understanding the Function of Internet Addressing
When using the Internet, you are assigned a unique Public IPv4 or IPv6 address, such as 42.44.146.127 or 2000:a8b6:7bc3:5e43:ee17:de2a:fcda:e8d0. You can verify this information at https://test-ipv6.com/. However, explaining these addresses, along with MAC addresses like 05:2d:c2:74:db:10, can be challenging for individuals who are not well-versed in technology. Moreover, this method lacks historical data, especially from past issues.
Navigating the Internet
To access a website, such as https://durgan.org, your computer communicates with a DNS server to convert the URL’s host section (durgan) and Top Level Domain (org) into an IP address, like 2.127.99.133. Each web request from your computer and browser includes the user-agent information, such as Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
The default gateway assigned to your computer is usually an automatically configured address obtained through DHCP, such as 10.80.50.31 (typically ending in .1 or .254 based on the scope size). This is the point where your computer forwards all its traffic to be routed elsewhere. For a detailed explanation on IPv6 connectivity, refer to our in-depth guide at how-to-fix-ipv6-connectivity/. On Mac or Linux systems, you can verify this information 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 10.80.50.31 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:a2f5:b089:18a3:cd2e%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): {103.149.184.46, 82.5.240.31}
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 05:2d:c2:74:db:10
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 f2:3b:fc:37:35:3a
}
Resolving Issues with Wired and Wireless Connections
When transferring data to your router, you have the option of using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.4, 11.2.9, or 12.0.4, there are various 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 transitioning to remote work and embracing the Work From Anywhere (WFA) approach.
Utilizing Pre-Installed Scripts
One useful tool in OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings in the CLI and can also generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many are specific to a certain point in time and are related to wireless, similar to wdutil.
You can run sudo nohup /usr/bin/sysdiagnose -u & in the background, and it will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will display 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. Just be mindful of the file sizes, which are around 300MB or less.
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