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I have several CentOS instances on Amazon's AWS/EC2 . The instances are able to ping each other, but not SNMP or traceroute among themselves . More data: I stopped iptables ...
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  1. #1
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    Question Need help: Amazon's AWS/EC2 CentOS instances cannot talk to each other


    I have several CentOS instances on Amazon's AWS/EC2.
    The instances are able to ping each other, but not SNMP or traceroute among themselves.
    More data:
    • I stopped iptables on all machines.
    • Each instance is able to traceroute and talk SNMP to itself.
    • Addresses of two of the machines: 10.152.143.130 10.211.155.240



    Can you suggest where the problem may lie?

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    I take it these are not VPC instances? Have you tried using VPC instances with the two machines in the same subnet? For traceroute to work you man need to enable and configure DNS services on these machines. Also, what does the 'route' command show on each machine?
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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    Do you have the proper ports open in your Security Group (on the AWS side) It is not enough to handle security internally on the Linux side, you must also allow the ports open in the security group. When you do this, you can open ALL ports from a specific IP address. Open ALL on 10.152.143.130 from 10.211.155.240 and then the reverse, open ALL on 10.211.155.240 from 10.152.143.130. If you only have the one security group, then open all on that group for both IP addresses. Also, if you have elastic IPs for each machine, you may want to open those IPs instead, as they do not change.

    Please let me know if this is the issue, otherwise, we can further troubleshoot it.

    Quote Originally Posted by ronbarak View Post
    I have several CentOS instances on Amazon's AWS/EC2.
    The instances are able to ping each other, but not SNMP or traceroute among themselves.
    More data:
    • I stopped iptables on all machines.
    • Each instance is able to traceroute and talk SNMP to itself.
    • Addresses of two of the machines: 10.152.143.130 10.211.155.240



    Can you suggest where the problem may lie?

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