How Can I Check OSX Connectivity
Understanding the Functioning of Internet Addressing
In the realm of the internet, individuals are assigned with unique public IPv4 addresses such as 248.54.139.77 or IPv6 addresses like 2000:eb48:8bca:1231:14db:5da5:c332:962e. It is possible to verify these addresses by visiting https://test-ipv6.com/. However, conveying these addresses to those who do not possess a technical background, or articulating MAC addresses like 69:47:d5:e2:ad:75, can be susceptible to errors and swiftly become intricate. Furthermore, this approach fails to provide any historical data, particularly pertaining to past issues.
Navigating the Internet
When attempting to reach a webpage, say https://mayer.info, the initial step is to connect to a DNS server in order to convert the host segment (mayer) along with the Top Level Domain (info) of the URL to an IP address such as 214.42.16. 76. Your computer and browser sends its specified type in all web requests, for example Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
Significance of the Default Gateway
The default gateway is typically an automatically configured address acquired through DHCP. For instance, you may obtain a default gateway like 10.188.144. 32 (albeit they generally finish with .1 or .254 based on the scope size), which is where your computer directs all of its traffic to be routed onwards. If you desire to delve deeper into this concept for IPv6, you can refer to our comprehensive guide on how-to-fix-ipv6-connectivity/. Additionally, you can verify this on Mac or Linux using:
ifconfig | grep 'inet6 addr'
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 10.188.144.32 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:fea6:eb1:9b61:9aaa%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): {234.101.10.33, 87.241.227.116}
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 69:47:d5:e2:ad:75
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 99:7f:a2:4b:68:29
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Techniques for Apple macOS / OSX
Regardless of whether you are running OSX/macOS version 10.14.9, 11.6.1, or 12.2.9, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a continuous set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are in favor of remote work and Work From Anywhere (WFA) setups.
Utilizing Pre-Installed Scripts for Assistance
One particularly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can also be set up to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to generate a wide array of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u &, the tool will operate 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 use 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. Keep in mind that the file sizes tend to be around 300MB, more or less.
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