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The server works fine via the Amazon assigned DNS entry, but I cannot reach it (using a browser) via the Elastic IP address Amazon assigned the box. Ping does not work either. I am trying to confirm it is reachable before I add the IP address to my own DNS entries.

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migrated from stackoverflow.com Feb 3 '12 at 16:51

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Are you sure you're using your elastic IP and not your private, could-local IP? –  Piotr Justyna Feb 3 '12 at 16:34
    
@Robert - Hi, well the aws.*** address will not lookup via ping, (but works in the browser) so I am actually at a loss on how to find out. I tried ping and I tried a few internet sites that do a lookup. –  Guido Anselmi Feb 3 '12 at 16:42
    
@Piotr - Yep. It's the "Elastic IP Address" not the Private IP Address. It also is used by Amazon in the header for the status tabs. –  Guido Anselmi Feb 3 '12 at 16:43
    
Guido, does it have a public DNS and instance ID assigned? –  Piotr Justyna Feb 3 '12 at 16:46
    
@Piotr - Yes. And the public DNS is reachable via a browser. Currently I am working behind a firewall, not sure if that will affect.....just attempted to ping a known site (msn.com) and that failed. Tethering my phone... –  Guido Anselmi Feb 3 '12 at 17:12

5 Answers 5

up vote 10 down vote accepted

Things to check:

  • Your elastic IP associated with your instance?
  • Your security group of instance permits incoming connections?
  • Your instance firewall permits incoming connections?
  • Your application listens?
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Just adding this reply as it might help other EC2 Newbies. If the Public DNS for your EC2 instance is: Public DNS: ec2-46-137-53-149.eu-west-1.compute.amazonaws.com you can access the instance using the numeric portion of the DNS Address. In the above case http://46.137.53.149/

Obviously you will need to have the relevant TCP Port open in the security group/profile associated with your instance as mentioned above.

The private IP (e.g. 10.235.47.101) is not accessible from outside the AWS network and is only useful when you have a cluster of EC2 nodes and want faster communication between them.

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Couple questions: what port are you trying to access? Do you have that port open on the security groups? Do you have an application listening on that port?

If I had to guess your security groups are not setup right. Make sure to open them to the correct ip addresses or to the world (0.0.0.0/0) if you are going access that port from multiple IPs.

If all that is not it, then dissociate and reallocate the IP to the instance.

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@Chan-da-man- Yes ports are open and there is an app listening. Exact same URL except domain name swapped with IP. –  Guido Anselmi Feb 3 '12 at 18:04
    
When you ping the full amazon cname does it come back with the elastic ip? –  chantheman Feb 4 '12 at 17:50

Also make sure Route table of VPC is set to enable IP address outside the VPC (0.0.0.0/0) to flow from the subnet to the Internet gateway.

Navigate to VPC > Route Tables ; Route tab. Check Destination is 'mapped' to Target Internet Gateway Id (apart from local).

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As others mentioned, the security group for your EC2 instance may not allow the HTTP port.

First,find the Security Group your instance is using.

enter image description here

Then, under Network & Security, go to the Security Groups section. Select your instance's security group and add an Inbound Custom TCP rule for Port range 80.

Security Groups in EC2

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