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I'm trying to set up NAT on a windows server 2008 r2 instance inside a VPC on AWS.

I've got two windows boxes, A and B

A has two network interfaces, one with an EIP attached and can connect to the internet fine.

B has its default gateway set to the private IP of As 2nd NIC (configured in RRAS as the private NIC)

All NICs are in a security group with all ports open.

I can RDP on to A, and from A to B, but A and B can't ping each other, and B can't route any traffic through A.

Tracerts timeout on every hop (they dont even hit B)

Any idea whats going wrong?


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I needed to disable source/dest check on A's 2nd interface.

Docs only say to do it on the instance. grrr

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I set up the NAT instance, but I can't ping instances inside my public or my private subnets. How did you disable source/dest on 2nd interface? – Aymeric Gaurat-Apelli Mar 26 '13 at 4:20

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