Martian packet
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In a computer network, packets with source addresses not routable by some computer on a network segment are referred to as martians or "packets from Mars", on the grounds that they are of no evident "terrestrial" (i.e. normal) source. Martian packets can arise from network equipment malfunction, misconfiguration of a host, or simple coexistence of two logical networks on a single physical layer. For instance, if the IP networks 192.168.34.0/24 and 10.2.3.0/24 operate on the same Ethernet segment, packets from 10.2.3.4 are Martians to the computer at 192.168.34.9, and vice versa.
Note that you may see packets from non-routable IP addresses when running the traceroute or tracepath commands. While packets cannot be routed to these routers, packets sent between 2 routers only need to know the address of the next hop within the local networks, which could be a non-routable address.