When ICMP redirect messages are sent

The switch is configured to send redirects by default. ICMP redirect messages are sent when one or more of the following scenarios occur:

  • The interface on which the packet comes into the router is the same interface on which the packet gets routed out.

  • 源IP地址的子网或网络on the same subnet or network of the next-hop IP address of the routed packet.

  • The datagram is not source-routed.

  • The destination unicast address is unreachable. In this case, the router generates the ICMP destination unreachable message to inform the source host about the situation.