How To Test OSX Internet
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 101.131.233.240 or an IPv6 address like 2000:46c8:4b1f:18fd:e208:e4ae:e7cc:34f9. The verification can be done at https://test-ipv6.com/. However, attempting to communicate these addresses to non-technical individuals or even mentioning MAC addresses like 8e:dc:2e:13:83:af can lead to errors and complexities. It also doesn’t provide any historical data, particularly related to previous issues that occurred.
Navigating the World Wide Web
When accessing a web page like https://pagac.co, the initial step involves contacting a DNS server to convert the host portion (pagac) together with the Top Level Domain (co) of the URL into an IP address like 243.13.203.32. Furthermore, your computer and browser send its type with all web requests, for example:
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
Typically, your default gateway is an automatically configured address via DHCP. For instance, you might have a default gateway like 192.168.206.96 (although they commonly end in .1 or .254 based on the scope size), and this is where your computer directs all its traffic to be routed. For in-depth information on IPv6, refer to how-to-fix-ipv6-connectivity/. To check on Mac or Linux, use the following:
<br>
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 192.168.206.96 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:bfcd:25cc:cbed:759b%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): {39.204.65.52, 168.186.82.153}
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 8e:dc:2e:13:83:af
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 3b:62:9f:22:b4:cc
}
Solutions for Wired and Wireless Network Issues
When it comes to transmitting data, you have the option to use a wired or wireless (Wi-Fi) medium at the physical and data layer towards your router.
Resolving Connectivity Problems on Apple macOS / OSX
No matter which version of OSX/macOS you’re running - whether it’s 10.13.3, 11.2.2, or 12.2.5, there are various troubleshooting tools available. However, these manual actions and scripts are unable to provide you with a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless related settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although it is primarily point-in-time only in relation to wireless, 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 for you. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose, which will trigger 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 keep in mind that the file sizes are around 300MB more or less.
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