CISCO-PTOPO-EXTN-MIB

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Organization: Cisco Systems, Inc.

Last Updated: 2002-05-12

Category: Cisco Devices, Network Monitoring (RMON)

Description: Extends physical topology discovery with Cisco-specific neighbor and connection data for network mapping.

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What Is CISCO-PTOPO-EXTN-MIB?

CISCO-PTOPO-EXTN-MIB is a Cisco extension to the IETF PTOPO-MIB (Physical Topology MIB), part of the network discovery and topology-mapping family of MIBs used across Cisco's routing and switching product line. It exposes data describing physical link connections between devices, specifically whether a discovered connection is bidirectional or unidirectional, and it adds a table for configuring dynamic topology learning via the Cisco Discovery Protocol (CDP). Rather than hardware health telemetry, its monitoring value lies in software/protocol status: the operational state of CDP-based discovery on a link, the row status of learned CDP connection entries, and the directionality classification of each physical connection, which helps detect misconfigured or asymmetric links. This module explicitly depends on and extends the base PTOPO-MIB and relies on CDP as its discovery mechanism. It is typically deployed in enterprise network management systems that build physical topology maps of Cisco switch and router fabrics for inventory and troubleshooting purposes, making the CISCO-PTOPO-EXTN-MIB MIB a standard component of CDP-based topology-mapping deployments.

IPNetwork Monitor allows you to monitor SNMP objects defined in CISCO-PTOPO-EXTN-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 switches
Cisco routers

Monitoring Examples

An administrator would poll cPtopoConnExtTable/cPtopoConnExtEntry to read cPtopoConnExtLinkDirection for each discovered link and confirm whether Cisco devices see a connection as bidirectional, since a mismatch can indicate a cabling or duplex issue. The cPtopoExtCdpTable exposes cPtopoExtCdpLocalChassis, cPtopoExtCdpLocalPort, and cPtopoExtCdpDiscoveryState, letting a monitoring tool verify that CDP-based dynamic learning is actively discovering neighbors on a given local port. If cPtopoExtCdpDiscoveryState shows a stalled or failed state, or cPtopoExtCdpRowStatus reveals stale entries, it signals that topology discovery on that interface has broken.

What Can Be Monitored

physical link directionality (bidirectional/unidirectional)
CDP discovery state per port
local chassis and port identifiers
CDP-learned connection row status
proxy interface for CDP discovery

Imported Objects

From CISCO-SMI

ciscoMgmt

OBJECT-IDENTITY

From ENTITY-MIB

PhysicalIndex

From IF-MIB

InterfaceIndexOrZero

From PTOPO-MIB

ptopoConnEntry

OBJECT-TYPE

From SNMPv2-CONF

MODULE-COMPLIANCE
OBJECT-GROUP

From SNMPv2-SMI

MODULE-IDENTITY
OBJECT-TYPE

From SNMPv2-TC

RowStatus

OIDs

OID symbolic	OID numeric	Type	Access	Description
ciscoPtopoExtnMIB	1.3.6.1.4.1.9.9.261			This MIB module contains extensions to the PTOPO-MIB that provide support to distinguish between bidirectional and unidirectional physical topology connections. It also introduces a table that allows configuration of dynamic learning of the physical topology through the Cisco Discovery Protocol (CDP).
ciscoPtopoExtnMIBObjects	1.3.6.1.4.1.9.9.261.1
cPtopoConnExtTable	1.3.6.1.4.1.9.9.261.1.1		not-accessible	This table augments the ptopoConnTable with information about the direction of physical network connections.
cPtopoConnExtEntry	1.3.6.1.4.1.9.9.261.1.1.1		not-accessible	An entry which contains additional information about the physical network connection contained in the ptopoConnEntry. It helps specify whether a remote connection endpoint is connected to the local port in the transmit direction, the receive direction or both directions.
INT cPtopoConnExtLinkDirection	1.3.6.1.4.1.9.9.261.1.1.1.1	INTEGER	read-create	The remote connection endpoint (identified by ptopoConnRemoteChassis and ptopoConnRemotePort of this row) may be connected to the local port (identified by ptopoConnLocalPort of this row) through either an unidirectional or bidirectional link. This object is used to indicate the directionality of the connection and in the case of unidirectional links this object indicates whether the remote connection endpoint is on the transmit or the receive link. For example, in case of optical interfaces where the transmitted and received signals travel on 2 different strands of fiber, it is possible that each fiber terminates at a different device. For instance, the transmit and receive fibers of the local port may be connected to different optical amplifiers. This object could then be used to indicate whether the remote device is on the transmit or the receive fiber of the local port. If the remote connection endpoint is connected to the transmit fiber of the local port then cPtopoConnExtLinkDirection is set to 'transmit'. If the remote connection endpoint is connected to the receive fiber of the local port then cPtopoConnExtLinkDirection is set to 'receive'. If both the transmit and receive fibers of the local port terminate at the same remote connection endpoint then this object is set to 'both'. Individual entries for 'transmit' and 'receive' should not be created in this case. Note that in the case of a port connected to a broadcast medium, there can be multiple entries associated with the port, with this object set to 'both'.
cPtopoExtCdpTable	1.3.6.1.4.1.9.9.261.1.2		not-accessible	This table contains a row for each local port (identified by the index of this table) for which the agent populates physical topology information (ptopoConnEntry) with neighbor information dynamically learned from the Cisco Discovery Protocol (CDP) running on this port or a proxy port.
cPtopoExtCdpEntry	1.3.6.1.4.1.9.9.261.1.2.1		not-accessible	This entry contains objects for configuring discovery of physical topology information for a local port (identified by the index of this entry) via CDP.
PHY cPtopoExtCdpLocalChassis	1.3.6.1.4.1.9.9.261.1.2.1.1	PhysicalIndex	not-accessible	The entPhysicalIndex value used to identify the chassis component associated with the local port for which physical topology information is discovered via CDP.
PHY cPtopoExtCdpLocalPort	1.3.6.1.4.1.9.9.261.1.2.1.2	PhysicalIndex	not-accessible	The entPhysicalIndex value used to identify the port component associated with the local port for which physical topology information is discovered via CDP.
INT cPtopoExtCdpDiscoveryState	1.3.6.1.4.1.9.9.261.1.2.1.3	INTEGER	read-only	This object indicates the state of physical topology discovery via CDP for the local port for which this row exists. The agent sets this object to 'cdpDisabled' if cPtopoExtCdpProxyIf is set to zero and CDP has not been configured to run on the local port, or if CDP has not been configured to run on the proxy interface whose ifIndex is given by the non-zero value in cPtopoExtCdpProxyIf. The enumeration 'interfaceDown' indicates that this interface is down, when cPtopoExtCdpProxyIf is set to zero, or the proxy interface is down, when cPtopoExtCdpProxyIf is set to a non-zero value. After this row has been activated, if CDP is running (on this or the proxy interface) and no neighbors have been discovered yet, the agent sets this object to 'waiting'. The 'discovered' state indicates that one or more neighbors have been discovered through CDP and the agent has accordingly created ptopoConnEntry(s) in the PTOPO-MIB.
NUM cPtopoExtCdpProxyIf	1.3.6.1.4.1.9.9.261.1.2.1.4	InterfaceIndexOrZero	read-create	Physical topology information for the local port (identified by cPtopoExtCdpLocalChassis and cPtopoExtCdpLocalPort of this row) can be discovered from CDP running on the local port, if it is CDP capable or from CDP running on a proxy interface. In the case of optical ports running wavelength division multiplexing, the physical connector port on which the CDP packet is transmitted is different from the logical interface representing the wavelength on which CDP is running. In such a case, physical topology for the 'external' optical port can be learned from CDP running on one of the wavelengths. This object is set to zero if physical topology information for the local port is discovered from CDP running on itself. Otherwise, this object contains the ifIndex value of the CDP capable interface which is being used as proxy to learn physical topology information for the local port. Usage of this object is possible only if the local port is the 'External Port', as specified in the CDP protocol, for the proxy interface. This object may be modified when the associated cPtopoExtCdpRowStatus object has a value of 'active'.
ROW cPtopoExtCdpRowStatus	1.3.6.1.4.1.9.9.261.1.2.1.5	RowStatus	read-create	This object is used to create and delete conceptual rows in the cPtopoExtCdpTable. Once this object has been set to 'active' it implies that physical topology discovery via CDP has been enabled for the local port for which this row exists. This object cannot be set to 'active' when any rows that were manually created for the local port exist in the ptopoConnTable. After this object is set to 'active', entries for this local port cannot be manually created in the ptopoConnTable. After the entry has been activated, this object cannot be set to any value other than 'destroy'. The row status never changes to 'notInService' after reaching the value 'active'.
cPtopoExtnConformance	1.3.6.1.4.1.9.9.261.3
cPtopoExtnCompliances	1.3.6.1.4.1.9.9.261.3.1
cPtopoExtnCompliance	1.3.6.1.4.1.9.9.261.3.1.1			The compliance statement for SNMP entities that implement the CISCO-PTOPO-EXTN-MIB.
cPtopoExtnGroups	1.3.6.1.4.1.9.9.261.3.2
cPtopoConnExtGroup	1.3.6.1.4.1.9.9.261.3.2.1			The collection of objects which augment the ptopoConnTable in the PTOPO-MIB.
cPtopoExtCdpGroup	1.3.6.1.4.1.9.9.261.3.2.2			The collection of objects which are required for configuration of physical topology discovery via CDP.
cPtopoExtCdpProxyGroup	1.3.6.1.4.1.9.9.261.3.2.3			The collection of objects which are used to configure physical topology learning via CDP with support for use of CDP running on a proxy interface.

RFC description

Cisco Physical Topology extension MIB; provides vendor-specific extensions to standard physical topology discovery and management.

Start monitoring Cisco switches / routers (physical topology discovery) with a free 30-day trial of IPNetwork Monitor. Import MIBs, browse SNMP OIDs, create custom SNMP monitors, configure alerts, and monitor any SNMP-enabled network device from a single console.

Download CISCO-PTOPO-EXTN-MIB

What Is CISCO-PTOPO-EXTN-MIB?

Supported Devices

Monitoring Examples

What Can Be Monitored

This MIB depends on

Related MIBs

RFC description