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    Enabling IP Source Address Validation

    Source address validation verifies that a packet has been sent from a valid source address. When a packet arrives on an interface, the router performs a routing table lookup using the source address. The result from the routing table lookup is an interface to which packets destined for that address are routed. This interface must match the interface on which the packet arrived. If it does not match, the router drops the packet.


    • Before you configure IP, you must create the lower-layer interfaces over which IP traffic flows.
    • All IP configurations will be removed from the interface when you issue the no ip interface command in Interface Configuration mode.

    To enable source address validation:

    • Issue the ip sa-validate command in Interface Configuration mode.
      host1(config-if)#ip sa-validate

      Use the no version to disable source address validation.

    Published: 2014-08-13