How Do You Test MacOS Internet
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a unique Public IPv4 or IPv6 address, such as 122.246.33.60 or 2000:bd9a:7a14:d1b5:2c88:8a41:93d:9bf6. These addresses can be verified on https://test-ipv6.com/. However, for those not well-versed in technology, conveying these addresses or MAC addresses like 82:b1:f0:8c:d5:38 can be prone to errors and quickly become complex. Additionally, this does not provide any historical data, especially when previous issues arise.
Navigating the Internet
When accessing a website such as https://reynolds.org, your computer first contacts a DNS server to convert the host (reynolds) and the Top Level Domain (org) of the URL into an IP address, such as 247.124.185.179. Furthermore, your computer and browser send their specifications with every web request, for example:
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically assigned address through DHCP, such as 192.0.0.66 (although they usually end in .1 or .254 depending on the scope). This is where your computer directs all its traffic to be forwarded. For IPv6, you can find more information on how-to-fix-ipv6-connectivity/, and you can verify it on Mac or Linux using the following command:
ip -6 route show
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 192.0.0.66 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:d13e:f77a:b437:a587%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): {193.145.111.27, 11.119.217.131}
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 82:b1:f0:8c:d5:38
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 27:f0:8d:4e:f8:a2
}
Solutions for Connectivity Issues
When it comes to transmitting data at the physical and data layer, you may encounter connectivity issues with either a wired or wireless (Wi-Fi) medium as you send data to your router.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are using, whether it’s ‘10.13.5’, ‘11.3.9’, or ‘12.1.9’, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless related settings to the command line interface and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs in a more comprehensive manner (although much of it is only relevant to wireless at a specific point in time, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (despite minimal interaction), 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 using Finder with Cmd+Shift+G. It’s important to be mindful of the file sizes, which are typically around 300MB.
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