Test MacOS Internet Connection
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 like 176.178.2.133 or an IPv6 like 2000:c395:6746:baaf:22c6:3737:41ad:fbc9. You can verify this at https://test-ipv6.com/. However, these addresses, including MAC addresses such as d5:69:02:77:94:fb, can be challenging for non-technical individuals to communicate and can lead to errors. Furthermore, they do not provide any historical data related to prior issues.
Navigating the World Wide Web
When accessing a webpage like https://bailey.com, you first connect to a DNS server to convert the host portion (bailey) along with the Top Level Domain (com) of the URL to an IP address like 44.197.237.137. Your computer and browser transmit their type along with all web requests, for example:
Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateway Usage
The default gateway is usually assigned automatically through DHCP and typically ends with .1 or .254, depending on the scope size, such as 172.25.174.161. This is where your computer directs all its traffic to be routed onwards. For IPv6, a comprehensive tutorial can be found at how-to-fix-ipv6-connectivity/, or on Mac or Linux operating systems using the following commands:
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 172.25.174.161 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:af23:ce2b:e433:9440%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): {180.13.70.221, 60.236.19.79}
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 d5:69:02:77:94:fb
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 69:51:3a:58:40:7b
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple’s macOS / OSX Platform
Regardless of the version of OSX/macOS you are operating on, whether it’s 10.13.1, 11.2.1, or 12.0.2, there are various tools available for troubleshooting. However, these manual actions and scripts fail to provide a series of interconnected values over time, which is where automated remote troubleshooting becomes essential, especially for teams involved in remote work and Work From Anywhere (WFA).
Effective Built-in Scripts for Troubleshooting
An extremely useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although many are only relevant to wireless issues, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can execute 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 or use Finder with Cmd+Shift+G to navigate to the path. However, be cautious of file sizes, as they can be around 300MB or more.
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