How Do You Test OSX Internet
Understanding Internet Protocol Addressing
When using the Internet, you are assigned an Internet Protocol (IP) address, which can be in the form of IPv4 or IPv6. An example of an IPv4 address is 241.148.30.147, while an IPv6 address looks like 2000:45b:afef:6708:8c5c:79d6:28f2:f820. This information can be verified using https://test-ipv6.com/. However, communicating these addresses, or even referencing MAC addresses such as 49:5f:b2:f1:de:53, can be challenging for those not familiar with technical jargon. Additionally, historical data is often important when troubleshooting past issues.
Navigating Through the World Wide Web
When attempting to access a website, such as https://will.name, the first step involves contacting a Domain Name System (DNS) server to convert the host (will) along with the Top Level Domain (name) of the URL into an IP address, for example, 171.43.242.81. Each web request also includes specific information about the device and browser being used, as shown by: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
The default gateway on a network is typically assigned automatically through the Dynamic Host Configuration Protocol (DHCP). It often ends with .1 or .254 depending on the scope size, for instance, 192.0.0.141, and serves as the point where all outgoing traffic from the computer is directed for further routing. For troubleshooting connectivity issues with IPv6, detailed instructions can be found in the blog post how-to-fix-ipv6-connectivity/. On Mac or Linux, the default gateway information can be obtained by running:
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 192.0.0.141 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:de3:4358:7d85:2118%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): {21.125.146.38, 140.21.57.214}
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 49:5f:b2:f1:de:53
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 78:74:26:0c:ac:3d
}
Solutions for Wired and Wireless Connectivity Issues
When it comes to sending data to your router, you have the option of using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
No matter which version of OSX/macOS you are running - whether it’s 10.12.5, 11.3.7, or 12.0.9 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) concept.
Useful Built-in Scripts
One particularly useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless-related settings to the CLI and can be configured to generate specific logs for troubleshooting. In addition, the more comprehensive sysdiagnose tool can be used to generate a wide range of logs, although much of the information is only point-in-time related to wireless, similar to wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u & in the background, the tool will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there is not much interaction), you can use 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. Keep in mind that the file sizes are around 300MB, more or less.
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