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Chapter 13
Unicast Reverse Path Forwarding
Opts:
Frags: 0 reassembled, 0 timeouts, 0 couldn't reassemble
Bcast: 331512 received, 0 sent
Mcast: 0 received, 0 sent
Sent:
Drop:
A nonzero value for the count of dropped or suppressed packets can mean one of two things:
Packets have a bad source address (normal operation).
•
Router is misconfigured to use Unicast RPF in environments where asymmetric routing exists; that
•
is, where multiple paths can exist as the best return path for a source address.
Note
Example 13-2
interface command.
Example 13-2 show ip interface Command
Router> show ip interface gigabitEthernet 8/1/0
GigabitEthernet8/1/0 is up, line protocol is up
Internet address is 80.1.1.1/24
Broadcast address is 255.255.255.255
Address determined by non-volatile memory
MTU is 1500 bytes
Helper address is not set
Directed broadcast forwarding is disabled
Outgoing access list is not set
Inbound
Proxy ARP is enabled
Local Proxy ARP is disabled
Security level is default
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
IP fast switching is enabled
IP Flow switching is disabled
IP CEF switching is enabled
IP CEF switching turbo vector
IP CEF turbo switching turbo vector
Associated unicast routing topologies:
IP multicast fast switching is enabled
IP multicast distributed fast switching is disabled
IP route-cache flags are Fast, CEF
Router Discovery is disabled
IP output packet accounting is disabled
IP access violation accounting is disabled
TCP/IP header compression is disabled
OL-2226-23
0 security failures, 0 bad options, 0 with options
0 end, 0 nop, 0 basic security, 0 loose source route
0 timestamp, 0 extended security, 0 record route
0 stream ID, 0 strict source route, 0 alert, 0 cipso, 0 ump
0 other
0 fragmented, 0 couldn't fragment
15 generated, 0 forwarded
0 encapsulation failed, 0 unresolved, 0 no adjacency
0 no route, 5 unicast RPF, 0 forced drop, 0 unsupported-addr
0 options denied, 0 source IP address zero
The RPF counter increases when the source address resolves to a NULL 0 because the address
is then considered as spoof.
shows the total of dropped or suppressed packets at a specific interface using the show ip
access list is not set
Topology "base", operation state is UP
Cisco 10000 Series Router Software Configuration Guide
Monitoring and Maintaining uRPF
13-15
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Table of Contents
Troubleshooting
