CISCO-NAT-EXT-MIB

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Organization: Cisco Systems, Inc.

Last Updated: 2006-06-05

Category: Cisco Devices, IP and Core Protocols, VPN and Security

Description: Extends NAT management with Cisco-specific address translation statistics and session tracking on Cisco routers.

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What Is CISCO-NAT-EXT-MIB?

CISCO-NAT-EXT-MIB extends the standard IETF NAT-MIB with Cisco-specific statistics for Network Address Translation on Cisco routers, adding detail beyond what the base NAT-MIB provides. It belongs to the IP address-translation/NAT networking area, exposing per-router address-translation statistics through cneAddrTranslationStatsTable. Its data is performance and capacity monitoring in nature: cneAddrTranslationNumActive and cneAddrTranslationNumPeak reveal current and historical peak concurrent NAT translations, while cneAddrTranslation1min/5min give short-term traffic-rate trending—together used to spot when a NAT device is approaching translation-table exhaustion, a common cause of dropped connections on address-translating edge routers. This module explicitly depends on and extends the standard NAT-MIB (RFC-based), so it should be interpreted alongside that base MIB. It is deployed on Cisco routers and firewalls performing NAT/PAT for internet edge, branch, or service-provider CGN (carrier-grade NAT) deployments. Network engineers evaluating or troubleshooting this functionality can download the CISCO-NAT-EXT-MIB file directly to load it into their MIB browser.

IPNetwork Monitor allows you to monitor SNMP objects defined in CISCO-NAT-EXT-MIB. Use the built-in SNMP Monitoring Browser to explore available variables, view their current values and descriptions, and select the objects you want to monitor. You can then create SNMP monitors, configure thresholds, and receive alerts when monitored values change.

Supported Devices

Cisco router
Cisco NAT/CGN edge device

Monitoring Examples

A network operator polls cneAddrTranslationStatsTable/cneAddrTranslationStatsEntry for cneAddrTranslationNumActive against cneAddrTranslationNumPeak to see how close a NAT gateway is to its historical maximum concurrent translation count. A sustained climb in cneAddrTranslation1min/5min rates alongside numActive approaching numPeak signals impending NAT pool or translation-table exhaustion, warranting capacity expansion before users start experiencing failed outbound connections.

What Can Be Monitored

active NAT translations count
peak NAT translations count
1-minute and 5-minute translation rate trends

Imported Objects

From CISCO-SMI

ciscoMgmt

OBJECT-IDENTITY

From ENTITY-MIB

entPhysicalIndex

OBJECT-TYPE

From SNMPv2-CONF

MODULE-COMPLIANCE
OBJECT-GROUP

From SNMPv2-SMI

Gauge32
MODULE-IDENTITY
OBJECT-TYPE
Unsigned32

How to Use in IPNetwork Monitor

Example using cneAddrTranslationNumActive OID:

Select a Cisco router or edge device as the target host to create a monitor — the SNMP service should be up and running on it. Click New Monitor, then check SNMP Custom on the Favorites tab, click Next, and confirm the host. On the next page, click Select... to open the built-in SNMP MIB Browser and type cneAddrTranslationNumActive into the Find box to locate it in the OID tree, selecting the specific row/instance you want to monitor since this is a table column, then select it and click OK. The total number of address translation entries that are currently available in the NAT device. On the monitor's Main parameters page you can set the target's SNMP port (default 161), credentials, polling interval, and other settings — see the SNMP Monitor help for details. On the State conditions and Alerting tabs, configure when the monitor should change state and trigger an alert; since this is a Gauge32-type OID, Value bounds is the most useful condition here — trigger an alert if the counter increases sharply between polls relative to its normal baseline (in Number of address translation entries), since an unexpected spike often reflects a real change in traffic or activity. Click Finish to create the monitor; you can adjust any parameter later.

OIDs

OID symbolic	OID numeric	Type	Access	Description
ciscoNATExtMIB	1.3.6.1.4.1.9.9.532			This MIB is an extension to the NAT-MIB. This MIB module includes objects for providing the NAT related statistics. Acronyms: NAT Network Address Translation.
ciscoNatExtMIBNotifs	1.3.6.1.4.1.9.9.532.0
ciscoNatExtMIBObjects	1.3.6.1.4.1.9.9.532.1
cneAddrTranslationStatsTable	1.3.6.1.4.1.9.9.532.1.1		not-accessible	A table of NAT statistics in a managed system.
cneAddrTranslationStatsEntry	1.3.6.1.4.1.9.9.532.1.1.1		not-accessible	An entry in the cneAddrTranslationStatsTable. This contains information about the NAT related statistics pertaining to a module. The entPhysicalIndex specifies the entry in entPhysicalTable with entPhysicalClass='module'.
G32 cneAddrTranslationNumActiveEx	1.3.6.1.4.1.9.9.532.1.1.1.1	Gauge32	read-only	The total number of address translation entries that are currently available in the NAT device. This indicates the aggregate of the translation entries created from both the static and dynamic address translation mechanisms.
U32 cneAddrTranslationNumPeak	1.3.6.1.4.1.9.9.532.1.1.1.2	Unsigned32	read-only	The maximum number of address translation entries that are active at any one time since the system startup. This indicates the high watermark of address translation entries that are active at any one time since the system startup. This object includes the translation entries created from both the static and dynamic address translation mechanisms.
G32 cneAddrTranslation1min	1.3.6.1.4.1.9.9.532.1.1.1.3	Gauge32	read-only	The averaged number of address translation entries which the NAT device establishing per second, averaged over the last 1 minute. This object includes the translation entries created from both the static and dynamic address translation mechanisms.
G32 cneAddrTranslation5min	1.3.6.1.4.1.9.9.532.1.1.1.4	Gauge32	read-only	The averaged number of address translation entries which the NAT device establishing per second, averaged over the last 5 minutes. This object includes the translation entries created from both the static and dynamic address translation mechanisms.
ciscoNatExtMIBConformance	1.3.6.1.4.1.9.9.532.2
ciscoNatExtMIBCompliances	1.3.6.1.4.1.9.9.532.2.1
ciscoNatExtMIBCompliance	1.3.6.1.4.1.9.9.532.2.1.1			The compliance statement for entities which implement the CISCO-NAT-EXT-MIB.
ciscoNatExtMIBGroups	1.3.6.1.4.1.9.9.532.2.2
ciscoNatExtAddrTransStatsGroup	1.3.6.1.4.1.9.9.532.2.2.1			This group contains the objects for NAT address translation related statistics.

RFC description

Extends NAT MIB with statistics for Network Address Translation on Cisco platforms.

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Download CISCO-NAT-EXT-MIB