Route Table Return Traffic Impact

Question

How does a Route Table handle return traffic? Is it going to follow what's in the route table? Will it review its list of destination/source and send via that path instead of what it came in on?

Say traffic comes in on 192.168.1.0/24 from some local endpoint.
The Route Table says to send all 192.168.1.0/24 traffic to NAT-xxxx; which is clearly not where the traffic came in from.
Will it go back out its endpoint, or via the NAT?

Accepted Answer

Route tables will look into the destination and next hop.

In your case scenario,

Traffic sourced from 192.168.1.0/24 --> NAT GW translate this into x.x.x.x --> return traffic comes from x.x.x.x >>>> NAT GW would translate this back to 192.168.1.0/24 (here the NAT GW looks into its route table for 192.168.1.0/24 and send the traffic to the local host.

Answer

Say traffic comes in on 192.168.1.0/24 from some local endpoint. The Route Table says to send all 192.168.1.0/24 traffic to NAT-xxxx; which is clearly not where the traffic came in from. Will it go back out its endpoint, or via the NAT?

It means traffic source is endpoint ENI (network interface ) IP address and Destination is 192.168.1.0/24 towards NAT-xxxx.

When NAT-xxx need to reply. It will see NAT-XX VPC route table and look for route of Endpoint ENI and send packet. ( In most of the case if Endpoint is in VPC then it will be Local route within VPC xxx/x LOCAL. Kind of switching/broadcast)

Route Table Return Traffic Impact

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