CISCO-IP-URPF-MIB Support
First Published: December 4, 2006
Last Updated: September 10, 2010
The CISCO-IP-URPF-MIB support provides Simple Network Management Protocol (SNMP) notification when a specified drop-rate threshold on a managed device is exceeded. You can use the IP Unicast Reverse Path Forwarding (RPF) feature to avert denial of service (DoS) attacks by verifying the validity of the source IP of an incoming packet. You can configure the Unicast RPF drop-rate threshold globally for a device or per interface.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for CISCO-IP-URPF-MIB Support" section.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
•Prerequisites for CISCO-IP-URPF-MIB Support
•Restrictions for CISCO-IP-URPF-MIB Support
•Information About CISCO-IP-URPF-MIB Support
•How to Configure Unicast RPF Drop-Rate Notification
•Configuration Examples for CISCO-IP-URPF-MIB Support
•Additional References
•Feature Information for CISCO-IP-URPF-MIB Support
Prerequisites for CISCO-IP-URPF-MIB Support
Before you configure CISCO-IP-URPF-MIB, you must configure the following features:
•Cisco Express Forwarding switching
•IP routing
•SNMP
•Unicast RPF
Restrictions for CISCO-IP-URPF-MIB Support
•Because Cisco IOS software does not support VPN routing and forwarding (VRF)-specific Unicast RPF counters, it does not support the following MIB objects related to VRF:
–cipUrpfIfVrfName
–cipUrpfVrfName
–cipUrpfVrfIfDrops
–cipUrpfVrfIfDiscontinuityTime
•This implementation of the CISCO-IP-URPF MIB supports only IPv4.
Information About CISCO-IP-URPF-MIB Support
•Implementation of Unicast RPF Notification
•Elements of Unicast RPF Notification
Implementation of Unicast RPF Notification
Unicast RPF is a security feature that verifies the validity of the source IP of an incoming packet. When a packet arrives at an interface and its source IP is unknown in the routing table or is a known bad source address, Unicast RPF drops the packet. IP verification of the source is done to prevent the DoS attacks by detecting problems with the incoming packets on an interface. However, deploying Unicast RPF without some automated monitoring capability is a challenge.
The CISCO-IP-URPF-MIB lets you specify a Unicast RPF drop-rate threshold on interfaces of a managed device that will send an SNMP notification when the threshold is exceeded. The MIB includes objects for specifying global and per-interface drop counts and drop rates and a method to generate SNMP traps when the drop rate exceeds a configurable per-interface threshold.
Although you can configure some parameters globally, you must configure the CISCO-IP-URPF-MIB on individual interfaces.
Elements of Unicast RPF Notification
The elements described in the following sections make Unicast RPF drop-rate notification work:
•Drop-Rate Computation
•Global Scalars
•Global Tables
•How to Configure Unicast RPF Drop-Rate Notification
•Per-Interface Configuration
Drop-Rate Computation
Whenever Unicast RPF is configured on an interface, the drop-rate calculation is done periodically (at intervals specified by the cipUrpfComputeInterval object). Drop rates are computed over a constantly sliding window, whose period starts at the configured number of seconds before the calculation and ends with the performance of the calculation.
Global Scalars
The following global scalars affect how the MIB agent computes all drop rates and generates notifications:
•cipUrpfDropRateWindow—This object specifies the window of time in the recent past over which the drop rate computation occurs. If there was no window (that is, the window is the epoch since booting up), an identical drop count burst at a later time would produce a lower drop rate than the one occurring earlier.
•cipUrpfComputeInterval—This object specifies how often the drop-rate computation occurs.
•cipUrpfDropNotifyHoldDownTime—This object specifies the minimum time between notifications for a particular packet flow on an interface.
Global Tables
The CISCO-IP-URPF-MIB includes the following global tables:
•cipUrpfTable—This table contains the global drop count and drop-rate objects per packet flow. These global rates are useful for quickly determining whether the managed device had Unicast RPF activity at a specific time.
•cipUrpfVrfTable—This table contains the index drop counters by VRF (if a VRF routing table is used to determine Unicast RPF checking). The table provides a method for VRF to index all the Unicast RPF-enabled interfaces.
Per-Interface Configuration
The following MIB objects enable per-interface configuration:
•cipUrpfIfDropRateNotifyEnable—This object specifies whether the system produces the cipUrpfIfDropRateNotify notification because Unicast RPF has dropped version cipUrpfIfIpVersion IP packets on the specified interface.
•cipUrpfIfNotifyDropRateThreshold—This object specifies the drop-rate threshold value above which a notification is generated.
Per-Interface Statistics
The following MIB objects track per-interface statistics:
•cipUrpfIfMonTable—This table contains the statistics for a particular packet flow on an interface.
•cipUrpfIfDrops—This object accumulates Unicast RPF drops on an interface. Snapshots of this value are used in the drop-rate computation. The computed drop rate is specified in the cipUrpfIfDropRate object. If Unicast RPF is configured on a subinterface, drop rates are computed.
How to Configure Unicast RPF Drop-Rate Notification
•Configuring Unicast RPF Drop-Rate Notification via Syslog (required)
•Configuring Unicast RPF Drop-Rate Notification via SNMP (required)
Configuring Unicast RPF Drop-Rate Notification via Syslog
Perform this task to configure the Unicast RPF drop-rate threshold and computation parameters for notification via syslog.
SUMMARY STEPS
1. enable
2. configure terminal
3. ip verify drop-rate compute window seconds
4. ip verify drop-rate compute interval seconds
5. ip verify drop-rate notify hold-down seconds
6. interface type number
7. ip verify unicast notification threshold packets-per-second
8. end
9. show ip interface type number
10. debug ip verify mib
DETAILED STEPS
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Step 1 |
enable
Router> enable |
Enables privileged EXEC mode. •Enter your password if prompted. |
Step 2 |
configure terminal
Router# configure terminal |
Enters global configuration mode. |
Step 3 |
ip verify drop-rate compute window seconds
Router(config)# ip verify drop-rate compute window 60 |
Configures the period of time, in seconds, over which the Unicast RPF drop count used in the drop-rate computation is collected. •The range is from 30 to 300. The default is 300. Note The value for the compute window must be greater than or equal to that entered using the ip verify drop-rate compute interval command. |
Step 4 |
ip verify drop-rate compute interval seconds
Router(config)# ip verify drop-rate compute interval 60 |
Configures the interval of time, in seconds, between Unicast RPF drop-rate computations. •The range is from 30 to 300. The default is 30. Note The value for the compute interval must be less than or equal to that entered using the ip verify drop-rate compute window command. |
Step 5 |
ip verify drop-rate notify hold-down seconds
Router(config)# ip verify drop-rate notify hold-down 60 |
Configures the minimum time, in seconds, between Unicast RPF drop-rate notifications. •The range is from 30 to 300. The default is 300. |
Step 6 |
interface type number
Router(config)# interface ethernet 3/0 |
Configures an interface and enters interface configuration mode. |
Step 7 |
ip verify unicast notification threshold packets-per-second
Router(config-if)# ip verify unicast notification threshold 750 |
Configures the threshold value, in packets per second, which determines whether to send a Unicast RPF drop-rate notification. •The range is from 0 to 2147483647. The default is 1000. Note If you configure the threshold as 0, every packet drop triggers a notification. |
Step 8 |
end
Router(config-if)# end |
Returns to privileged EXEC mode. |
Step 9 |
show ip interface type number
Router# show ip interface ethernet 2/3 |
(Optional) Displays the verification drop rate and the number of verification drops when Unicast RPF is configured for an interface. |
Step 10 |
debug ip verify mib
Router# debug ip verify mib |
(Optional) Displays output that is useful for troubleshooting Unicast RPF notification. |
Configuring Unicast RPF Drop-Rate Notification via SNMP
Perform this task to configure the Unicast RPF drop-rate threshold and computation parameters for notification via SNMP.
SUMMARY STEPS
1. enable
2. configure terminal
3. ip verify drop-rate compute window seconds
4. ip verify drop-rate compute interval seconds
5. ip verify drop-rate notify hold-down seconds
6. interface type number
7. ip verify unicast notification threshold packets-per-second
8. snmp trap ip verify drop-rate
9. end
10. show ip interface type number
11. debug ip verify mib
DETAILED STEPS
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Step 1 |
enable
Router> enable |
Enables privileged EXEC mode. •Enter your password if prompted. |
Step 2 |
configure terminal
Router# configure terminal |
Enters global configuration mode. |
Step 3 |
ip verify drop-rate compute window seconds
Router(config)# ip verify drop-rate compute window 60 |
Configures the period of time, in seconds, over which the Unicast RPF drop count used in the drop-rate computation is collected. •The range is from 30 to 300. The default is 300. Note The value for the compute window must be greater than or equal to that entered using the ip verify drop-rate compute interval command. |
Step 4 |
ip verify drop-rate compute interval seconds
Router(config)# ip verify drop-rate compute interval 60 |
Configures the interval of time, in seconds, between Unicast RPF drop-rate computations. •The range is from 30 to 300. The default is 30. Note The value for the compute interval must be less than or equal to that entered using the ip verify drop-rate compute window command. |
Step 5 |
ip verify drop-rate notify hold-down seconds
Router(config)# ip verify drop-rate notify hold-down 60 |
Configures the minimum time, in seconds, between Unicast RPF drop-rate notifications. •The range is from 30 to 300. The default is 300. |
Step 6 |
interface type number
Router(config)# interface ethernet 3/0 |
Configures an interface and enters interface configuration mode. |
Step 7 |
ip verify unicast notification threshold packets-per-second
Router(config-if)# ip verify unicast notification threshold 750 |
Configures the threshold value, in packets per second, which determines whether to send a Unicast RPF drop-rate notification. •The range is from 0 to 2147483647. The default is 1000. Note If you configure the threshold to be 0, every packet drop triggers a notification. |
Step 8 |
snmp trap ip verify drop-rate
Router(config-if)# snmp trap ip verify drop-rate |
Configures the router to send an SNMP notification when the Unicast RPF drop rate exceeds the configured threshold. |
Step 9 |
end
Router(config-if)# end |
Returns to privileged EXEC mode. |
Step 10 |
show ip interface type number
Router# show ip interface ethernet 2/3 |
(Optional) Displays the verification drop rate and the number of verification drops when Unicast RPF is configured for an interface. |
Step 11 |
debug ip verify mib
Router# debug ip verify mib |
(Optional) Displays output that is useful for troubleshooting Unicast RPF notification. |
Configuration Examples for CISCO-IP-URPF-MIB Support
•Example: Configuring Unicast RPF Drop-Rate Notification via Syslog
•Example: Configuring Unicast RPF Drop-Rate Notification via SNMP
•Example: Verifying and Troubleshooting the Unicast RPF Configuration
Example: Configuring Unicast RPF Drop-Rate Notification via Syslog
The following example shows how to configure Unicast RPF drop-rate notification via syslog:
Router# configure terminal
Router(config)# ip verify drop-rate compute window 60
Router(config)# ip verify drop-rate compute interval 60
Router(config)# ip verify drop-rate notify hold-down 60
Router(config)# interface ethernet 3/0
Router(config-if)# ip verify unicast notification threshold 750
Example: Configuring Unicast RPF Drop-Rate Notification via SNMP
The following example shows how to configure Unicast RPF drop-rate notification via SNMP:
Router# configure terminal
Router(config)# ip verify drop-rate compute window 60
Router(config)# ip verify drop-rate compute interval 60
Router(config)# ip verify drop-rate notify hold-down 60
Router(config)# interface ethernet 3/0
Router(config-if)# ip verify unicast notification threshold 750
Router(config-if)# snmp trap ip verify drop-rate
Example: Verifying and Troubleshooting the Unicast RPF Configuration
The following is sample output from the show ip interface command. The output displays the verification drop rate and the number of verification drops when Unicast RPF is configured for an interface. The last five lines in the following example show the output of the show ip interface command when Unicast RPF is configured:
Router# show ip interface ethernet 2/3
Ethernet2/3 is up, line protocol is up
Internet address is 10.10.5.4/16
Broadcast address is 255.255.255.255
Address determined by non-volatile memory
Helper address is not set
Directed broadcast forwarding is disabled
Outgoing access list is not set
Inbound access list is not set
Local Proxy ARP is disabled
Security level is default
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
IP fast switching is disabled
IP Flow switching is disabled
IP CEF switching is disabled
IP multicast fast switching is disabled
IP multicast distributed fast switching is disabled
IP route-cache flags are No CEF
Router Discovery is disabled
IP output packet accounting is disabled
IP access violation accounting is disabled
TCP/IP header compression is disabled
RTP/IP header compression is disabled
Probe proxy name replies are disabled
Policy routing is disabled
Network address translation is disabled
WCCP Redirect outbound is disabled
WCCP Redirect inbound is disabled
WCCP Redirect exclude is disabled
BGP Policy Mapping is disabled
IP verify source reachable-via RX, allow default
0 suppressed verification drops
The following is sample output from the debug ip verify mib command. The command displays output that is useful for troubleshooting Unicast RPF notification:
Router# debug ip verify mib
01:29:45: cipUrpfScalar_get, searchType 161
01:29:45: ipurpfmib_get_scalars
01:29:45: cipUrpfScalar_get, searchType 161
01:29:45: cipUrpfScalar_get, searchType 161
01:29:45: ipurpfmib_get_scalars
01:29:45: cipUrpfScalar_get, searchType 161
01:29:45: cipUrpfScalar_get, searchType 161
01:29:45: ipurpfmib_get_scalars
01:29:45: cipUrpfScalar_get, searchType
161ipurpfmib_get_urpf_entryipurpfmib_get_urpf_entryipurpfmib_get_urpf_entryipurpfmib_get_
urpf_entry
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
01:29:45: cipUrpfIfMonEntry_get, searchType 161
01:29:45: ipurpfmib_get_urpf_ifmon_entry entry: ST 161, if 1, ip 1
Additional References
Related Documents
MIBs
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CISCO-IP-URPF-MIB |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs |
RFCs
Technical Assistance
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The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
http://www.cisco.com/cisco/web/support/index.html |
Feature Information for CISCO-IP-URPF-MIB Support
Table 1 lists the features in this module and provides links to specific configuration information.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 1 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Table 1 Feature Information for CISCO-IP-URPF-MIB Support
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CISCO-IP-URPF-MIB Support |
12.2(31)SB2 12.2(33)SRC 12.4(20)T 12.2(33)SXI2 |
The CISCO-IP-URPF-MIB provides SNMP notification when a specified drop-rate threshold on a managed device is exceeded. You can use the IP Unicast RPF feature to avert DoS attacks by verifying the validity of the source IP of an incoming packet. You can configure the Unicast RPF drop-rate threshold globally for a device or per interface. The following commands were introduced or modified: debug ip verify mib, ip verify drop-rate compute interval, ip verify drop-rate compute window, ip verify drop-rate notify hold-down, ip verify unicast notification threshold, show ip interface, snmp trap ip verify drop-rate |
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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