Public IP Address

What Is

A Public IP address is an IP address that is universally unique. (In IPv4 lingo, a class A, B, or C address in the PUBLIC ranges of addresses, versus PRIVATE ranges.)

Find Yours

To find out what is the public IP address of a network, the uplink / northbound interface of the router connecting to the Internet, there are many resources on the Internet that can help:

GUI, Web-based (Find One, For Default Gateway)

This method is great when someone asks for which you have, when someone is adding you to some site that uses public IP address as part of authentication and information security solutions.

CLI, Command Line (Scripts, For Many Interfaces)

 

 

  • List all available interfaces:
    • ifconfig
  • List which interfaces that are active:
    • for i in $(ifconfig -lu); do if ifconfig $i | grep -q “status: active” ; then echo $i; fi; done

 

From one location (SATX), have multiple (2) public interfaces, one local and one via VPN:

mbp17:~ $ curl --interface en0 http://checkip.amazonaws.com/ 
136.50.145.111
mbp17:~ $ curl --interface en11 http://checkip.amazonaws.com/ 
185.236.41.131

From another location (ATX), with one public interface at this time, but doing some time comparisons:

mbp17:~ $ time curl --interface en0 http://checkip.amazonaws.com/ 
183.174.114.213
real 0m0.119s
user 0m0.005s
sys 0m0.006s
mbp17:~ $ time curl --interface en0 ifconfig.me
183.174.114.213
real 0m0.098s
user 0m0.006s
sys 0m0.006s

Another location

mbp17:~ $ time curl --interface en0 http://checkip.amazonaws.com/ 
183.174.114.213

real 0m0.547s
user 0m0.007s
sys 0m0.008s
mbp17:~ $ time curl --interface en8 http://checkip.amazonaws.com/ 
183.174.114.213

real 0m0.320s
user 0m0.006s
sys 0m0.006s
mbp17:~ $ time curl --interface utun8 http://checkip.amazonaws.com/ 
193.32.210.122

real 0m0.538s
user 0m0.005s
sys 0m0.006s
mbp17:~ $

##

 

mbp17:~ johan$ speedtest 
speedtest: Found 5 active interface(s) to work with ( en0 en7 en8 en15 utun8 )
Retrieving speedtest.net configuration...
Testing from Spectrum (173.174.114.227)...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by Windstream (Dallas, TX) [280.46 km]: 21.379 ms
Testing download speed................................................................................
Download: 114.53 Mbit/s
Testing upload speed................................................................................................
Upload: 11.58 Mbit/s

real 0m23.961s
user 0m3.203s
sys 0m2.640s
2021-10-28 08:44:13 CDT MBP17 en0 WiFi:jphm2_5GHz 192.168.0.167 Download: 114.53 Mbit/s Upload: 11.58 Mbit/s public_ip: 173.174.114.227 
speedtest: interface en7 is LINK-LOCAL (169.254.100.108) - NOT handling for speedtesting
Retrieving speedtest.net configuration...
Testing from Spectrum (173.174.114.227)...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by Windstream (Dallas, TX) [280.46 km]: 18.408 ms
Testing download speed................................................................................
Download: 8.18 Mbit/s
Testing upload speed................................................................................................
Upload: 6.32 Mbit/s

real 0m24.374s
user 0m2.461s
sys 0m1.278s
2021-10-28 08:44:38 CDT MBP17 en8 Ethernet 192.168.0.14 Download: 8.18 Mbit/s Upload: 6.32 Mbit/s public_ip: 173.174.114.227 
Retrieving speedtest.net configuration...
Testing from Spectrum (173.174.114.227)...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by Windstream (Dallas, TX) [280.46 km]: 21.481 ms
Testing download speed................................................................................
Download: 7.85 Mbit/s
Testing upload speed................................................................................................
Upload: 6.49 Mbit/s

real 0m24.116s
user 0m2.344s
sys 0m1.240s
2021-10-28 08:45:02 CDT MBP17 en15 Ethernet 10.32.128.102 Download: 7.85 Mbit/s Upload: 6.49 Mbit/s public_ip: 173.174.114.227 
Retrieving speedtest.net configuration...
Testing from Hydra Communications Ltd (193.32.210.122)...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by Lightning Fibre Ltd (London) [6.55 km]: 121.404 ms
Testing download speed................................................................................
Download: 85.02 Mbit/s
Testing upload speed................................................................................................
Upload: 7.87 Mbit/s

real 0m28.223s
user 0m2.671s
sys 0m1.703s
2021-10-28 08:45:31 CDT MBP17 utun8 (TBD) 10.5.0.2 Download: 85.02 Mbit/s Upload: 7.87 Mbit/s public_ip: 193.32.210.122 (DEFAULT ROUTE)
mbp17:~ johan$