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https://issues.apache.org/jira/browse/CLOUDSTACK-10346?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16636595#comment-16636595
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ASF GitHub Bot commented on CLOUDSTACK-10346:
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izenk commented 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
if two vms are in on 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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