Troubleshoot OSX Internet Connection
Understanding the Functionality of Internet Addressing
When using the Internet, you are assigned a specific IP (Internet Protocol) address, which comes in the form of public IPv4 or IPv6. This unique identifier can be checked using a reliable tool like https://test-ipv6.com/, but it can be quite challenging for non-technical individuals to communicate or even remember these addresses. Additionally, there is a lack of historical data associated with these addresses, especially during past issues.
Navigating the World Wide Web
In order to access a website, such as https://lynch.net, your computer connects to a DNS (Domain Name System) server to convert the URL into an IP address, which is essential for accessing the site. Furthermore, your computer’s web requests always include its browser and operating system details, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
Significance of Default Gateways
The default gateway, typically obtained automatically through DHCP (Dynamic Host Configuration Protocol), serves as the destination for all outgoing traffic from your computer. The default gateway, often ending with .1 or .254 depending on the network size, is crucial for routing network traffic. For troubleshooting IPv6 connectivity on Mac or Linux, you can refer to our detailed guide at how-to-fix-ipv6-connectivity/.
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 192.0.0.69 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:a9b3:7aa7:af66:bbf3%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): {117.245.245.220, 7.197.252.243}
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 1b:b7:cc:f8:25:70
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 60:41:e1:1f:1a:db
}
Resolving Issues with Wired and Wireless Connections
When it comes to sending data to your router, the choice between using a wired or wireless (Wi-Fi) medium occurs at the physical and data layer.
Strategies for Resolving Issues on Apple macOS / OSX
Regardless of whether you are using OSX or macOS versions such as 10.15.6, 11.2.2, or 12.1.7, there are various troubleshooting tools available. However, these tools do not provide a series of correlated values over time, which can be a limitation. Automated remote troubleshooting becomes particularly useful for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Pre-installed Scripts for Assistance
On OSX/macOS, the sudo wdutil info tool is quite beneficial as it provides a dump to the CLI of current wireless settings and can be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool offers a more comprehensive approach, generating a wide range of logs, although many are only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. Alternatively, running sudo /usr/bin/sysdiagnose interactively will result in a privacy warning and provide the option to navigate to the location where the logs are saved. However, it’s important to be mindful of the file sizes, which can be around 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 🏠🏝🛰.
