Troubleshoot Mac Internet
The Fundamentals of Internet Addressing
In the world of the Internet, there are two types of IP addresses that you might come across. The first is a Public IPv4 address, which looks something like 184.84.234.85, and the second is an IPv6 address, which appears as 2000:9df9:888:7973:f181:ffbd:2a2a:ba7b. You can verify your address at https://test-ipv6.com/. However, it can be quite challenging for individuals who are not tech-savvy to convey or even identify these addresses. This becomes even more complex when dealing with MAC addresses like 28:33:a7:6f:5f:35. Furthermore, this method does not provide any historical data, particularly when faced with previous issues.
Navigating Through the World Wide Web
Accessing a website, such as https://fisher.io, begins with reaching out to a DNS server to translate the host portion (fisher) combined with the Top Level Domain (io) of the URL into an IP address, such as 42.95.125.46. Notably, your computer and web browser disclose their type with every web request, as shown by this example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Understanding the Significance of Default Gateways
Ordinarily, your default gateway is an address that is automatically configured via DHCP. For instance, you may receive a default gateway like 192.168.31.70 (although they typically end in .1 or .254 based on the scope size), which serves as the destination for all traffic from your computer to be routed. Details on troubleshooting IPv6 connectivity are available at how-to-fix-ipv6-connectivity/. Additionally, you can perform checks on Mac or Linux using the following command:
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 192.168.31.70 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 fe80:11e7:4f7a:8114:a165%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): {95.6.43.179, 108.195.66.13}
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 28:33:a7:6f:5f:35
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 5a:43:b6:af:97:e7
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you have - be it 10.13.7, 11.6.3, or 12.2.7, there are various tools available for resolving connectivity issues. However, these tools and manual actions do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that operate remotely and embrace the concept of Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool in OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the command line interface 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, albeit most of the information related to wireless is only relevant to a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and generate logs, use the command sudo nohup /usr/bin/sysdiagnose -u &, which will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose, which will display a privacy warning and open Finder in the correct location. Alternatively, you can navigate to the /var/tmp directory using Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
