EC2's EIP port 443 not working

Question

Hi everyone,

I have an EC2 instance with Ubuntu  and an attached Elastic IP (EIP), and services running on ports 443 and 3000. The security group settings are as follows:
| Port range | Protocol | Source |
| --- | --- | --- |
| 22 | TCP | 10.0.0.0/8 |
| 3000 | TCP | 10.0.0.0/8 |
| 443 | TCP | 0.0.0.0/0 |

The problem is that when I use telnet to test the ports, 
for example:

$ telnet  internal IP:22 or $ telnet to the internal IP:3000, it works fine.

However, when I try to $ telnet EIP:443, it fails and returns a connection refused error.

When I try $ telnet internal IP:443, it works fine.

But the security group is configured with 0.0.0.0/0. Why can't I telnet to the EIP on port 443?

BTW, the ufw is inactive, and don't have iptables, Network ACL as follow:

| Rule number | Type | Protocol | Port range | Source | Allow/Deny |
| --- | --- | --- | --- | --- | --- |
| 100 | All traffic | ALL | ALL | 0.0.0.0/0 | Allow |
| * | All traffic | ALL | ALL | 0.0.0.0/0 | Deny |

Accepted Answer

Is there an Internet Gateway attached to the VPC or is it over a NAT Gateway? Can you access Internet from the instance? Here is a detail [troubleshooting list](https://repost.aws/knowledge-center/vpc-connect-instance).

Answer

Two things come to mind here, firstly do you have the security group associated with the new network interface that has the elastic IP atttached? https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/MultipleIP.html#MultipleIPReqs

> - You associate security groups with network interfaces, not individual IP addresses. Therefore, each IP address you specify in a network interface is subject to the security group of its network interface.

Second thing is around the software that is listening on port 443, is it set to listen on the IP address associated with the NIC to which the elastic IP is attached? Taking Apache as an example https://httpd.apache.org/docs/2.4/bind.html

Rule number	Type	Protocol	Port range	Source	Allow/Deny
100	All traffic	ALL	ALL	0.0.0.0/0	Allow
*	All traffic	ALL	ALL	0.0.0.0/0	Deny

EC2's EIP port 443 not working

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