Test OSX Internet Connection
Understanding Internet Addressing
When connecting to the internet, you are assigned a unique Public IPv4 address, such as 200.251.11.125, or an IPv6 address like 2000:2592:550e:6d9:633e:b74d:bfcb:fcc. These addresses can be verified by visiting https://test-ipv6.com/. However, for those who are not tech-savvy, communicating these addresses, or even referencing MAC addresses like d5:ff:e8:e2:8e:0b, can quickly become complex and error-prone. Furthermore, this method does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When accessing a web page, such as https://renner.com, the first step is to contact a DNS server to translate the host portion (renner) combined with the Top Level Domain (com) of the URL into an IP address, for example, 210.210.239.118. Additionally, your computer and browser include information about their types in all web requests, such as Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36.
The Significance of Default Gateways
The default gateway is typically an automatically assigned address via DHCP, such as 10.91.34.221 (often ending in .1 or .254 depending on the scope size). This is where your computer sends all its traffic to be routed onwards. For IPv6, there is a detailed discussion on how-to-fix-ipv6-connectivity/ available for Mac or Linux users.
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 10.91.34.221 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 fe80:9eeb:6cc7:719f:68e9%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): {195.198.69.229, 65.78.233.216}
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 d5:ff:e8:e2:8e:0b
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 b5:a8:03:4e:eb:e3
}
Diagnosing Connectivity Issues on macOS
When it comes to troubleshooting wired or wireless connectivity on Apple macOS, there are a variety of methods and tools that can be used. Whether you are using an older version like 10.15.6 or the latest 12.2.7, there are options available to help identify and resolve connectivity issues, especially important for remote work and Work From Anywhere (WFA) scenarios.
Utilizing Native Tools for Troubleshooting
One valuable built-in tool for troubleshooting on macOS is the sudo wdutil info command, which provides a dump of current wireless settings and can be configured to generate specific logs for further analysis. Additionally, the sysdiagnose tool can be used to generate a comprehensive set of logs, although it is primarily focused on point-in-time observations related to wireless connectivity.
For running sysdiagnose in the background, the command sudo nohup /usr/bin/sysdiagnose -u & can be utilized, which will write logs to /var/tmp/<blah>.tar.gz. Alternatively, running sudo /usr/bin/sysdiagnose interactively will provide a privacy warning and open Finder in the correct location, allowing for easy access to the generated logs for analysis. It’s important to note that the file sizes can be substantial, around 300MB or more.
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