After forwarding a packet, by default, a router can send a neighbor redirect message to a host to inform it of a better first-hop router. The host receiving the neighbor redirect message will then readdress the packet to the better router.
A router sends a neighbor redirect message only for unicast packets, only to the originating node, and to be processed by the node.
A neighbor redirect message has a value of 137 in the Type field of the ICMP packet header.