Ingress and Egress Filtering

There's a lot of confusion with ingress and egress filtering on routers, lets see what it really is:

Ingress Filtering:
Ingress filtering is a technique used to make sure that incoming packets are actually from the networks that they claim to be from(Do not allow spoofing).

Ingress filtering allows you to control the traffic that enters your network and restrict activity to legitimate purposes.

Egress Filtering:
Egress filtering controls the traffic headed out of your network.

1. No inbound traffic bears a source IP address assigned to your network.
2. No inbound traffic bears a private (non-routable) IP address.

Just remember the following details and you will be good to go, just make sure you have both types of filtering enabled on your firewalls / routers to have a secure network, it helps thwarf DoS attacks, Spoofing attacks and Connect back to external IP Addreses if one of your internal machines is compromised.

-- Anish