This is A Draft
Describe EliezerCroitoru/Drafts/rp_filter here.
What is Reverse Path
Routing networks are complex since in many cases networks traffic is "non-symetric".
In symetric networks the traffic from one network to another has a known path which is known by all participating routers.
In asymetric(aka non-symetric) networks the traffic towards specific network can flow towards the target inside a network which just forwards the traffic closer to the target by assuming that the choosen path is the best.
It can be an instruction by the admin or by an algorighm which the admin applied.
The result can be that two packets from the same connection which by definition is the same "tcp flow" (as an example) can be routed towards the targer from 10 different ports of the target network edge router.
So there is only one or two(number for the example) routers in the Internet that should publish a subnet to be theirs and by that all traffic towards this subnet will flow towards them. There is no restriction for this traffic to flow symetricly towards the target host.
A reverse path is a path, or can be sometimes identified by the router "port", that is not the main for the router traffic to flow throw towards the network.
As an example a router that has 3 interfaces with 3 IP addresses and which interface 1 is the main traffic pipe of the network but also this router allows another path of incomming packets towards it's network.