RFC 1180, "TCP/IP tutorial", January 1991Source of RFC: Legacy
Area Assignment: int
Errata ID: 5074
Publication Format(s) : TEXT
Reported By: Erik Auerswald
Date Reported: 2017-07-29
Section 5.3 says:
When an incoming IP packet arrives it is never forwarded back out through the same network interface.
It should say:
When an incoming IP packet arrives it may be forwarded back out through the same network interface.
IP routers can and do send IP packets out the ingress interface. An ICMP redirect message may be sent in this case.
This is different to Ethernet bridge behavior, where a frame will not be sent out the ingress interface.
An IP packet that egresses the ingress interface is carried in a new Ethernet frame, this is not the same frame that arrived at the ingress interface (different SRC and DST MAC addresses, decreased TTL in the IP header).