How Can I Check OSX IP Settings
Explaining Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 15.98.188.20 or an IPv6 address like 2000:572e:6dd:e9c0:8f3e:ee4a:6324:912a. This information can be verified by visiting https://test-ipv6.com/. However, for those who are not knowledgeable in technology, communicating these addresses, or even mentioning MAC addresses like a9:1a:86:65:6e:59, can be prone to errors and become complex quite rapidly. Furthermore, this does not provide any historical data, particularly when dealing with past issues.
Navigating the Internet
When trying to access a website such as https://wolff-barrows.com, the initial step involves contacting a DNS server to convert the host name (wolff-barrows) along with the Top Level Domain (com) of the URL into an IP address like 171.56.105.58. In all web requests, your computer and browser actually send this type e.g. Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Understanding the Significance of Default Gateways
Your default gateway is typically an address that is automatically configured via DHCP. You receive a default gateway like 10.120.231.102 (although they usually end in .1 or .254 depending on the scope size) and this is where your computer sends all its traffic to be routed onwards. For IPv6, a more detailed explanation can be found in our article how-to-fix-ipv6-connectivity/ but you can verify on Mac or Linux 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 10.120.231.102 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 fe80:244a:8fa0:5f28:e3f0%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): {254.133.165.140, 213.86.244.187}
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 a9:1a:86:65:6e:59
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 54:2f:b2:3e:88:4a
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Strategies for Apple macOS / OSX
Regardless of whether you are using OSX/macOS versions such as 10.11.1, 11.0.6, or 12.0.2, there is a wide range of troubleshooting tools available. However, these manual methods and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that practice remote work and Work From Anywhere (WFA).
Utilize the Embedded Scripts
An incredibly useful tool for OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool offers a more comprehensive option for generating a variety of logs, though much of it is only relevant to wireless settings, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run, you can use sudo /usr/bin/sysdiagnose, but be cautious of the large file sizes of approximately 300MB.
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