[EC2] Why no Public IPv4, but can go to the Internet?

Question

[ec2-user@ip-10-16-60-224 ~]$ **route**

Kernel IP routing table

```
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

default         ip-10-16-48-1.a 0.0.0.0         UG    0      0        0 eth0

10.16.48.0      0.0.0.0         255.255.240.0   U     0      0        0 eth0

instance-data.a 0.0.0.0         255.255.255.255 UH    0      0        0 eth0

```

[ec2-user@ip-10-16-60-224 ~]$

[ec2-user@ip-10-16-60-224 ~]$ **ip add**

1: lo:  mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo

valid_lft forever preferred_lft forever

inet6 ::1/128 scope host

valid_lft forever preferred_lft forever

2: eth0:  mtu 9001 qdisc pfifo_fast state UP group default qlen 1000

link/ether 06:bf:f7:bd:36:52 brd ff:ff:ff:ff:ff:ff

inet 10.16.60.224/20 brd 10.16.63.255 scope global dynamic eth0

valid_lft 3109sec preferred_lft 3109sec

inet6 2406:da18:e26:a403:977:a307:147f:a413/128 scope global dynamic

valid_lft 437sec preferred_lft 127sec

inet6 fe80::4bf:f7ff:febd:3652/64 scope link

valid_lft forever preferred_lft forever

[ec2-user@ip-10-16-60-224 ~]$

[ec2-user@ip-10-16-60-224 ~]$ **traceroute 1.1.1.1**

traceroute to 1.1.1.1 (1.1.1.1), 30 hops max, 60 byte packets

1  ec2-18-141-171-15.ap-southeast-1.compute.amazonaws.com (18.141.171.15)  8.342 ms ec2-175-41-128-177.ap-southeast-1.compute.amazonaws.com (175.41.128.177)  7.433 ms ec2-18-141-171-1.ap-southeast-1.compute.amazonaws.com (18.141.171.1)  19.818 ms

2  100.65.32.224 (100.65.32.224)  3.347 ms 100.65.33.240 (100.65.33.240)  13.093 ms 100.65.34.176 (100.65.34.176)  23.462 ms

3  100.66.16.74 (100.66.16.74)  7.746 ms 100.66.16.202 (100.66.16.202)  7.773 ms 100.66.16.38 (100.66.16.38)  3.531 ms

4  100.66.19.190 (100.66.19.190)  5.059 ms 100.66.19.180 (100.66.19.180)  7.843 ms 100.66.18.228 (100.66.18.228)  16.918 ms

5  100.66.7.249 (100.66.7.249)  12.221 ms 100.66.6.247 (100.66.6.247)  10.830 ms 100.66.6.113 (100.66.6.113)  21.846 ms

6  100.66.4.89 (100.66.4.89)  80.326 ms 100.66.4.159 (100.66.4.159)  18.434 ms 100.66.4.9 (100.66.4.9)  11.122 ms

7  100.65.11.1 (100.65.11.1)  0.604 ms 100.65.9.97 (100.65.9.97)  0.322 ms  0.358 ms

8  203.83.223.30 (203.83.223.30)  1.243 ms 150.222.108.77 (150.222.108.77)  1.575 ms 52.93.10.76 (52.93.10.76)  1.316 ms

9  52.93.8.160 (52.93.8.160)  2.001 ms 150.222.108.66 (150.222.108.66)  1.870 ms 150.222.108.68 (150.222.108.68)  2.114 ms

10  52.93.11.127 (52.93.11.127)  1.386 ms 52.93.11.115 (52.93.11.115)  1.350 ms 52.93.11.125 (52.93.11.125)  1.338 ms

11  99.83.90.55 (99.83.90.55)  4.053 ms  4.046 ms 99.83.68.227 (99.83.68.227)  4.297 ms

12  172.70.140.3 (172.70.140.3)  2.673 ms * 172.70.144.5 (172.70.144.5)  2.274 ms

13  one.one.one.one (1.1.1.1)  1.755 ms  1.795 ms  1.771 ms

Thank you very much.

Answer

An EC2 instance only has a local network interface and knows nothing about its public IP; that public IP is set up in the Internet Gateway (IGW)'s NAT table, mapped to the instance's local IP address.  If the instance is in a public subnet with routing to the IGW then it will have public access.  Of course it could also be set up in a private/NAT subnet with outbound internet access via routing to a NAT Gateway or NAT Instance.

[EC2] Why no Public IPv4, but can go to the Internet?

Relevant content