Martian Packet
As martian packet (German as: "data packet from Mars," "a Marsianers data packet") or short martian ( martian, martian ) are called data packets whose source address is not in the network, in which they were observed routable is. The name is derived from the fact that this data packet (from the point of view of the observer) “cannot come from here” or, in other words: There are no indications that the packet comes from this (our) world. It is obvious - following this line of thought - to assume that it comes from Mars.
Martian packets can arise due to malfunction or frequent incorrect configuration of hosts as well as in regular operation when several logical networks are operated on a physical network segment (a collision domain ). They also arise when the Internet protocol is attacked.
Other definitions only consider IP packets with the source address of the test loopback interface [127.0.0.1] as martian packets .
example
The IP networks 192.168.34.0/24 and 10.2.3.0/24 are operated on the same Ethernet segment. The host with the IP address 192.168.34.9 sees IP packets from 10.2.3.4 as coming from Mars , and vice versa.