Check OSX Connectivity
Explanation of Internet Addressing
When using the Internet, individuals may have a Public IPv4 address such as 144.126.20.135 or an IPv6 address like 2000:b42:2062:5341:1cf9:62f:7c48:4fdd. Verification of this information can be done at https://test-ipv6.com/. Communicating these addresses, or even referring to MAC addresses like 64:9f:12:8d:c4:d7, can be prone to errors and quickly becomes complex. Furthermore, historical data is not readily accessible, especially when dealing with past issues.
How Web Pages are Accessed
In order to access a web page like https://wilderman-schneider.org, the first step is to contact a DNS server to convert the combination of the host portion (wilderman-schneider) and the Top Level Domain (org) of the URL into an IP address such as 142.61.19.163. Each web request from your computer and browser includes information about its type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
The default gateway is typically an address automatically configured via DHCP. An ordinary default gateway may appear as 192.168.174.169 (although they often end with .1 or .254, depending on the scope size) and serves as the point to which your computer forwards all its traffic for routing. A more detailed explanation on IPv6 can be found at how-to-fix-ipv6-connectivity/, and on Mac or Linux, it can be verified with:
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 192.168.174.169 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 fe80:3441:50:a53:b7b8%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): {63.235.214.213, 31.59.34.246}
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 64:9f:12:8d:c4:d7
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 80:b6:69:83:02:26
}
Fixing Connectivity Issues: Wired vs Wireless
When it comes to the physical and data layer, you have the option to use either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using - whether it’s 10.12.3, 11.0.8, or 12.2.5 - 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 essential, especially for teams that adopt remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can 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 & in the background will write logs to /var/tmp/<blah>.tar.gz for you. For an interactive run (though there isn’t much interaction), you can use sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, and you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. Just be cautious of the file sizes, which are approximately 300MB.
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