How Do You Test MacOS No-access
Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 196.127.40.167 or an IPv6 address like 2000:6caf:21b9:862:91a3:5e04:a223:ab79. This information can be verified by visiting the test-ipv6 website. However, conveying these addresses or MAC addresses like 9a:a4:e3:0b:5b:9d to individuals who are not technologically savvy can become prone to errors and complexity. Furthermore, this method does not provide any historical data, particularly when resolving past issues.
Navigating to Websites
To access a webpage such as https://johnson.com, you first reach out to a DNS server to convert the host component (johnson) along with the Top Level Domain (com) of the URL into an IP address like 139.192.85.187. Your computer and browser discloses its type during all web requests, e.g.
Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Significance of Default Gateways
By default, your gateway is typically an automatically configured address through DHCP. Usually, you receive a default gateway like 172.16.13.8 (although they often end in .1 or .254 based on the scope size). This is where your computer forwards all its traffic to be routed further. For IPv6, in-depth guidelines are provided in our article on how to rectify IPv6 connectivity. Alternatively, you can verify this on Mac or Linux systems using the following code:
//verify gateway for IPv6
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 172.16.13.8 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:ef41:6387:2417:1b5a%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): {34.27.137.207, 33.141.59.68}
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 9a:a4:e3:0b:5b:9d
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 77:dd:09:71:28:b8
}
Problem Solving for Wired and Wireless Networks
When it comes to transferring data to your router, you have the option of using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Users
Regardless of which version of OSX/macOS you are running, whether it’s 10.13.6, 11.4.5, or 12.3.7, there are various troubleshooting tools available. However, the manual actions and scripts may not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are engaged in remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs, although much of it pertains to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there isn’t much interaction), you can use sudo /usr/bin/sysdiagnose and it will give a privacy warning. Running it without the background process should open Finder in the correct location, or you can navigate to /var/tmp manually, or use Finder with Cmd+Shift+G to locate the path. Just keep in mind that the file sizes are around 300MB.
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