How Do You Understand Apple Connectivity
Understanding the Functionality of Internet Addressing
When using the Internet, it is common to receive either a Public IPv4 or IPv6 address. These addresses can be checked using a tool such as https://test-ipv6.com/. However, translating these addresses and communicating them to non-technical individuals can be error-prone and complex. Furthermore, it does not provide any historical data, particularly pertaining to past issues.
Navigating the World Wide Web
Accessing a webpage involves initially contacting a DNS server to convert the host part of the URL to an IP address. For example, the URL https://runolfsson.biz may translate to the IP address 142.212.176.13. When making web requests, your computer and browser also provide information about their type, such as: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Recognizing the Significance of Default Gateways
The default gateway, typically obtained automatically via DHCP, serves as the address where your computer routes all of its traffic. For IPv6, details on how to check this can be found in our blog post how-to-fix-ipv6-connectivity/. On Mac or Linux, it can be verified using:
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 10.33.147.13 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:c9b9:627a:55ef:a6fe%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): {99.48.247.186, 129.92.9.126}
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 a2:7d:18:11:78:cb
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 ec:bd:eb:a1:f2:49
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you might be using a medium that is either wired or wireless (Wi-Fi) at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are on OSX or macOS versions such as 10.12.2, 11.2.9, or 12.1.9, 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, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One particularly useful tool on OSX/macOS is the sudo wdutil info, 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, 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. For an interactive run (though there is not much interaction), you can execute sudo /usr/bin/sysdiagnose and it will provide 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. However, be aware of the file sizes, which are approximately 300MB more or less.
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