Check Mac IP Settings
The Functionality of IP Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 243.123.166.234 or an IPv6 address like 2000:7a:f7d1:91c8:f73a:b63b:2bb6:606b. An easy way to check this is through https://test-ipv6.com/. However, for those less knowledgeable about technology, communicating these addresses, or even referencing MAC addresses like e4:8a:98:da:04:3d, can quickly become complex and prone to errors. Additionally, this method does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When visiting a webpage, such as https://auer-wiegand.name, your first step involves accessing a DNS server to convert the host portion (auer-wiegand) combined with the Top Level Domain (name) of the website to an IP address like 31.28.123.41. In each web request, your computer and browser send their type, for instance: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
Normally, your default gateway is an auto-assigned address via DHCP. This gateway, such as 192.0.0.129 (although it typically ends in .1 or .254 based on the scope size), is where your computer directs all its traffic to be routed further. As for IPv6, more details can be found in our article how-to-fix-ipv6-connectivity/ or by checking on Mac or Linux 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 192.0.0.129 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 fe80:7647:9a97:6698:c4a6%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): {11.57.160.56, 195.145.40.226}
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 e4:8a:98:da:04:3d
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 c8:52:59:2a:9b:4b
}
Resolving Issues with Wired or Wireless Connections
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Strategies for Apple macOS / OSX Troubleshooting
Regardless of whether you are running 10.14.2, 11.5.4, or 12.1.7, there are various tools available to assist with troubleshooting. However, these manual methods and scripts do not provide a sequence of correlated values over time. This is where automated remote troubleshooting becomes particularly valuable, especially for teams that are adapting to remote work and embracing the concept of Work From Anywhere (WFA).
Useful Native Scripts
A helpful tool for OSX/macOS is sudo wdutil info, which generates a dump of current wireless settings in the CLI and can be configured to produce specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to generate a comprehensive range of logs, although much of it is only related to wireless settings and is point-in-time data like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there is not much interaction), you can execute sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to access the path. Keep in mind that the file sizes are approximately 300MB or more.
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