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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CLOUDSTACK-10346) Problem with NAT configuration and VMs not accessing each other via public IPs
Date Wed, 03 Oct 2018 08:27:00 GMT

    [ https://issues.apache.org/jira/browse/CLOUDSTACK-10346?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16636597#comment-16636597
] 

ASF GitHub Bot commented on CLOUDSTACK-10346:
---------------------------------------------

izenk edited a comment on issue #2514: [CLOUDSTACK-10346] Problem with NAT configuration and
VMs not accessing each other via public IPs
URL: https://github.com/apache/cloudstack/pull/2514#issuecomment-426552700
 
 
   @rhtyd may be this helps..
   Looks like routing goes in such way, that packets do not go through SNAT rule on VR, what
leads to such situation:
   if two vms are in one TIER and vm1 wants to connect to vm2 through PUBLIC IP, it should
look like:
   vm1 internal ip -> VR SNAT -> VR DNAT -> vm2 internal ip
   **now on vm2 I can see packets from vm1, but** source ip is set to vm1 internal ip (not
VR SNAT)
   
   So if I try telnet from vm1 to VR publicIP:80 (which is forwarded to vm2:80), on vm2 I
can see packets on port 80, but these packets are from vm1 internal ip. Next, **I even can
see replies from vm2 on vm1**, but because this replies are coming from vm2 directly to vm1:internal
ip and not from VR (how it should be), in fact connection is not established
   

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> Problem with NAT configuration and VMs not accessing each other via public IPs
> ------------------------------------------------------------------------------
>
>                 Key: CLOUDSTACK-10346
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-10346
>             Project: CloudStack
>          Issue Type: Bug
>      Security Level: Public(Anyone can view this level - this is the default.) 
>            Reporter: Rafael Weingärtner
>            Assignee: Rafael Weingärtner
>            Priority: Major
>
> When users create a VPC, and configure a NAT from a public IP to application in a VM.
This VM(applications) are not accessible via public IP for other VMs in the same VPC.
>  
> The problem is in the NAT table. If you take a closer look at rules, you will see something
like:
> {code:java}
> -A PREROUTING -d publicIP/32 -i eth1 -p tcp -m tcp --dport 80 -j DNAT --to-destination
internalIp:80
> {code}
> The problem is that according to this rule only packets coming via eth1(public interface),
will be “redirected” to the internal IP. We need an extra entry to each one of the NAT
configurations. For the presented rule, we would need something like:
> {code:java}
> -A PREROUTING -d publicIP/32 -i eth2 -p tcp -m tcp --dport 80 -j DNAT --to-destination
internalIp:80
> {code}



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