Contents
- CISCO-IP-URPF-MIB Support
- Finding Feature Information
- Prerequisites for CISCO-IP-URPF-MIB Support
- Restrictions for CISCO-IP-URPF-MIB Support
- Information About CISCO-IP-URPF-MIB Support
- Implementation of Unicast RPF Notification
- Elements of Unicast RPF Notification
- Drop-Rate Computation
- Global Scalars
- Global Tables
- Per-Interface Configuration
- Per-Interface Statistics
- How to Configure Unicast RPF Drop-Rate Notification
- Configuring Unicast RPF Drop-Rate Notification via Syslog
- Configuring Unicast RPF Drop-Rate Notification via SNMP
- 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
- Additional References
- Feature Information for CISCO-IP-URPF-MIB Support
CISCO-IP-URPF-MIB Support
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
- 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
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
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
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
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
- Configuring Unicast RPF Drop-Rate Notification via SNMP
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.
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
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.
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
| Command or Action | Purpose | |||
|---|---|---|---|---|
| Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode.
| ||
| Step 2 |
configure
terminal
Example: Router# configure terminal |
Enters global configuration mode. | ||
| Step 3 |
ip
verify
drop-rate
compute
window
seconds
Example: 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.
| ||
| Step 4 |
ip
verify
drop-rate
compute
interval
seconds
Example: Router(config)# ip verify drop-rate compute interval 60 |
Configures the interval of time, in seconds, between Unicast RPF drop-rate computations.
| ||
| Step 5 |
ip
verify
drop-rate
notify
hold-down
seconds
Example: Router(config)# ip verify drop-rate notify hold-down 60 |
Configures the minimum time, in seconds, between Unicast RPF drop-rate notifications.
| ||
| Step 6 |
interface
type
number
Example: Router(config)# interface ethernet 3/0 |
Configures an interface and enters interface configuration mode. | ||
| Step 7 |
ip
verify
unicast
notification
threshold
packets-per-second
Example: 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.
| ||
| Step 8 |
snmp
trap
ip
verify
drop-rate
Example: 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
Example: Router(config-if)# end |
Returns to privileged EXEC mode. | ||
| Step 10 |
show
ip
interface
type
number
Example: 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
Example: 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> enable 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)# i nterface ethernet 3/0 Router(config-if)# ip verify unicast notification threshold 750 Router(config-if)# end
Example Configuring Unicast RPF Drop-Rate Notification via SNMP
The following example shows how to configure Unicast RPF drop-rate notification via SNMP:
Router> enable 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 Router(config-if)# end
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 interfacecommand 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 MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set 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 disabled IP Flow switching is disabled IP CEF switching is disabled IP Null turbo vector IP Null turbo vector 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 Input features: uRPF IP verify source reachable-via RX, allow default 0 verification drops 0 suppressed verification drops 0 verification drop-rate Router#
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
|
Related Topic |
Document Title |
|---|---|
|
Cisco IOS commands |
|
|
Security commands |
Cisco IOS Security Command Reference |
|
Configuring Unicast RPF |
“Configuring Unicast Reverse Path Forwarding” module in the Cisco IOS Security Configuration Guide: Securing the Data Plane |
|
Configuring SNMP |
“Configuring SNMP Support” module in the Network Management Configuration Guide |
MIBs
|
MIB |
MIBs Link |
|---|---|
|
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: |
RFCs
|
RFC |
Title |
|---|---|
|
None |
-- |
Technical Assistance
|
Description |
Link |
|---|---|
|
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. |
Feature Information for CISCO-IP-URPF-MIB Support
The following table provides release information about the feature or features described in this module. This table 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.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
|
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
CISCO-IP-URPF-MIB Support |
12.2(31)SB2 12.2(33)SRC 12.4(20)T 12.2(33)SXI2 12.2(50)SY |
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 |