How To Understand Apple Internet Connection
Understanding How Internet Addressing Functions
When connected to the Internet, you are assigned a unique Public IPv4 address, such as 72.10.186.174, or an IPv6 address like 2000:4f88:7b6b:50e9:3e10:f0c6:c697:bb7e. To verify these addresses, you can visit https://test-ipv6.com/. However, for individuals who are not well-versed in technology, attempting to communicate these addresses can be error-prone and complex, especially when dealing with MAC addresses like b8:f1:2c:e3:13:7a. Furthermore, this method does not provide any historical data, which is particularly important in identifying prior issues.
Navigating the World Wide Web
Accessing a website, such as https://klein.info, involves initially contacting a DNS server to convert the host portion (klein) in combination with the Top Level Domain (info) of the URL into an IP address like 119.173.47.119. In every web request, your computer and browser send their types, for instance: 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 generally assigned as an automatically configured address through DHCP, such as 192.0.0.150 (although they usually end in .1 or .254 based on the scope size). This is where your computer forwards all of its traffic to be routed further. Check how to fix IPv6 connectivity on Mac or Linux by visiting: how-to-fix-ipv6-connectivity/.
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 192.0.0.150 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 fe80:62e1:5083:2d74:b23c%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): {193.196.136.181, 11.169.162.190}
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 b8:f1:2c:e3:13:7a
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 27:98:d9:a7:37:f5
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS version 10.11.5, 11.2.6, or 12.3.7, there are various troubleshooting tools available. However, these tools do not provide a series of correlated values over time, which is essential for remote troubleshooting, especially for teams working remotely or embracing Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings in the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs related to wireless issues, although most are only relevant to a specific point in time, similar to the wdutil tool.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. Alternatively, you can run the tool interactively with sudo /usr/bin/sysdiagnose and it will display a privacy warning. When run interactively, the log files should open in Finder or you can navigate to the /var/tmp location using Finder. Keep in mind that the file sizes are approximately 300MB.
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