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Document double nat scenario for OpenStack deployments #806

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Jul 27, 2022
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Document double nat scenario for OpenStack deployments #806

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Document double nat scenario for OpenStack deployments
sridhargaddam Jul 25, 2022
d786200
Merge branch 'devel' into issue-805
dfarrell07 Jul 26, 2022
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24 changes: 22 additions & 2 deletions src/content/operations/nat-traversal/_index.en.md
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Expand Up @@ -356,9 +356,29 @@ NAT, or if other applications on the internal network were already using the 450
ports, the remote ends would not be able to contact gateway C or D over the expected ports.
{{% /notice %}}

### Double NAT Traversal
### Double NAT Traversal (scenario 1)

In this case case, A & B cluster gateways have direct reachability over their private
In this case, clusters C & D are neither reachable on their private IPs (192.168.0.4 and 192.168.0.4) nor
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Shouldn't it be 192.168.128.4 ?

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Why? The diagram uses 192.168.0.4

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Private IPs are the node-ips. As per the diagram its 192.168.0.4 (deliberately shown the same IPs as its possible in such deployments) and the private floating-ips are 10.2.0.1 and 10.2.0.2 respectively. The public-ip auto-discovery for such clusters would be the same for both (2.1.1.1).

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Ooops, I missed the diagram

on the public IP. However, they are reachable over the private floating IPs (10.2.0.1 and 10.2.0.2).
Submariner cannot detect these private floating IPs. To get the connectivity working, you can annotate
the Gateway node with the private floating IP as shown below.

![on-premises](/images/natt/double_nat_scenario1.png)

```bash
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Q : the annotated public IP (e.g: 10.2.0.1) will be used as EP's public IP for all connections (including to clusters C,D) , can you elaborate how the connection from cluster A to C will work ?

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@sridhargaddam sridhargaddam Jul 27, 2022 •
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There is no Cluster A in this topology. Please look at the next scenario and it is currently not supported in Submariner.

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Ack, 10x

kubectl annotate node $GWC gateway.submariner.io/public-ip=ipv4:10.2.0.1
kubectl annotate node $GWD gateway.submariner.io/public-ip=ipv4:10.2.0.2

# restart the gateways to pick up the new setting
for cluster in C D;
do
kubectl delete pod -n submariner-operator -l app=submariner-gateway --kubeconfig $cluster
done
```

### Double NAT Traversal (scenario 2)
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In this case, A & B cluster gateways have direct reachability over their private
IPs (10.0.0.1 and 10.1.0.1) possibly with large MTU capabilities, while between cluster
C and D (192.168.0.4 and 192.168.0.4 too), reachability over the private IPs is not possible
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but it would be possible over the private floating IPs 10.2.0.1 and 10.2.0.2. However Submariner
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