Cisco Systems 6500, EA6500 Configuring the Unicast RPF Checking Mode

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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
78-14099-04
Chapter 23 Configuring Network Security
Configuring Unicast Reverse Path Forwarding
This example shows how to enable self-pinging:
Router(config)# interface gigabitethernet 4/1
Router(config-if)# ip verify unicast source reachable-via any allow-self-ping
Router(config-if)# end
Configuring the Unicast RPF Checking Mode
There are two Unicast RPF checking modes:
• Strict checking mode, which verifies that the source IP address exists in the FIB table and verifies
that the source IP address is reachable through the input port.
• Exist-only checking mode, which only verifies that the source IP address exists in the FIB table.
Note The most recently configured mode is automatically applied to all ports configured for Unicast RPF
checking.
To configure Unicast RPF checking mode, perform this task:
When configuring the Unicast RPF checking mode, note the following syntax information:
• Use the rx keyword to enable strict checking mode.
• Use the any keyword to enable exist-only checking mode.
• Use the allow-default keyword to allow use of the default route for RPF verification.
• Use the list option to identify an access list.
– If the access list denies network access, spoofed packets are dropped at the port.
– If the access list permits network access, spoofed packets are forwarded to the destination
address. Forwarded packets are counted in the interface statistics.
– If the access list includes the logging action, information about the spoofed packets is sent to
the log server.
Note When you enter the ip verify unicast source reachable-via command, the Unicast RPF checking mode
changes on all ports in the switch.
Command Purpose
Step 1 Router(config)# interface {{vlan vlan_ID} |
{type1 slot/port} | {port-channel number}}
1. type = ethernet, fastethernet, gigabitethernet, or tengigabitethernet
Selects an interface to configure.
Note Based on the input port, Unicast RPF verifies the
best return path before forwarding the packet on
to the next destination.
Step 2 Router(config-if)# ip verify unicast source
reachable-via {rx | any} [allow-default] [list]
Configures the Unicast RPF checking mode.
Router(config-if)# no ip verify unicast Reverts to the default Unicast RPF checking mode.
Step 3 Router(config-if)# exit Exits interface configuration mode.