Cisco Cisco IOS Software Release 12.0(13)S7

To enable Unicast Reverse Path Forwarding (Unicast RPF) for IPv6, use the ipv6 verify unicast 
reverse-path command in interface configuration mode. To disable Unicast RPF, use the no form of this 
command.

ipv6 verify unicast reverse-path [access-list name]

no ipv6 verify unicast reverse-path [access-list name] 

Unicast RPF is disabled.

Interface configuration

The Unicast RPF for IPv6 feature requires that Cisco Express Forwarding for IPv6 (CEFv6) is enabled 
on the router.

On a Cisco 12000 series Internet router, the ipv6 verify unicast reverse-path command is used to enable 
Unicast RPF for IPv6 in strict checking mode.

Beginning in Cisco IOS Release 12.0(31)S, the Cisco 12000 series Internet router supports both the ipv6 
verify unicast reverse-path and ipv6 verify unicast source reachable-via rx commands to enable 
Unicast RPF to be compatible with the Cisco IOS Release 12.3T and 12.2S software trains.

Use the ipv6 verify unicast reverse-path command to mitigate problems caused by malformed or 
forged (spoofed) IP source addresses that pass through a router. Malformed or forged source addresses 
can indicate denial-of-service (DoS) attacks based on source IP address spoofing.

access-list name 

 (Optional) Specifies the name of the access list. 

This keyword and argument are not supported on the Cisco 12000 
series Internet router.

12.2(13)T

This command was introduced.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.0(31)S

This command was integrated into Cisco IOS Release 12.0(31)S and 
introduced on the 10G Engine 5 SPA Interface Processor in the Cisco 12000 
series Internet router. 

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.