Understand Apple Internet Connection
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 246.79.82.177 or an IPv6 address like 2000:dd1d:9a60:9dfe:120c:5e3d:a9eb:7266. You can verify this information at https://test-ipv6.com/. Communicating and recognizing these addresses, along with MAC addresses like f9:c6:b9:df:9d:42, can be challenging for individuals who are not technically inclined. Furthermore, these addresses do not provide historical data, especially when addressing past issues.
Navigating the World Wide Web
In order to access a website like https://fadel.co, your computer reaches out to a DNS server to translate the host name portion (fadel) combined with the Top Level Domain (co) of the URL into an IP address, such as 9.177.82.127. Whenever your computer and browser send web requests, they include information about their types, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
Typically, your default gateway is an automatically assigned address through DHCP. This default gateway, such as 10.216.215.25 (commonly ending in .1 or .254 based on scope size), is where your computer directs all of its traffic to be routed. For a more in-depth explanation on IPv6, you can refer to how-to-fix-ipv6-connectivity/. 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 10.216.215.25 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 fe80:35bf:d444:1c0e:634f%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): {114.155.91.238, 130.134.197.254}
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 f9:c6:b9:df:9d:42
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 6f:e4:49:91:50:a3
}
Troubleshooting Connectivity Issues
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) connection at the physical and data layer.
Resolving Connectivity Problems on Apple macOS / OSX
No matter which version of OSX/macOS you are using, whether it’s 10.14.6, 11.4.8, or 12.1.1, there are various tools available for resolving connectivity issues. However, these tools may not provide a series of connected values over time, making automated remote troubleshooting particularly useful for remote work and Work From Anywhere (WFA) environments.
Useful Built-in Scripts
A helpful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can generate a wide range of logs, although many are only related to wireless settings and are only point-in-time data, similar to wdutil.
To run the sysdiagnose tool in the background and generate logs at /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose and follow the privacy warning prompt. When not running in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Cmd+Shift+G in Finder. Keep in mind that the file sizes can be around 300MB.
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