Cloud NAT with IP Forwarding

[shuaib]

Hi,

So I'm dealing with a very very specific case.

Essentially we have a proxy VM/server.

This proxy VM has 3 NICs, one VPC for egress, one VPC for ingress and one VPC called management.

Example subnets:

10.0.1.0/24 - management

10.0.3.0/24 - ingress

10.0.5.0/24 - egress

Now this proxy has IP forwarding enabled.

Further, a cloud NAT has been set up on the Egress VPC.

Egress works from the proxy VM.

Our VPN devices can connect to the proxy VM as well.

The devices are in the following subnet:

10.0.8.0/24

Given a set port, let us say 53000

The issue arises when our VPN connected device tries to use the proxy VM for egress.

The VPC flow logs show that something from the 10.0.8.3:53000 is going to a destination but the destination does not pick it up.

Whereas the destination does pick it up when the it is sent from one of the internal VPC addresses.

[shuaib · Accepted solution]

Solution:

Use IP aliases in the subnet, VM & Cloud NAT.