How to add custom route via EC2?

Question

I need to route certain traffic via site-to-site VPN. This trivial thing doesn't work for me in AWS, while works fine in my test on-prem environment.
For instance:
- I need to route traffic to 111.111.111.111/32 via 10.10.10.11
- I tried both adding this route to 10.10.10.10, and adding it into the VPC routing table - no results. I.e. I. don't see packets to 111.111.111.111 coming to 10.10.10.11. (I checked both using network sniffer on 10.10.10.11 and using AWS Flow logs).

Any ideas?
TIA,
Vitaly

Isaac Behrens · Answer

You should do this by routing to an AWS object that has the IP...  i.e. the eni-XXXX that has the 10.10.10.11 IP assigned to it.

AWS route tables need to point objects like ENIs, TGWs, PCXs and not IP addresses.

vitaly_il · Answer

I  found the issue - it was the default "Source/dest. check" == True in the ENI of my VPN box.

How to add custom route via EC2?

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