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The MPLS Label Switching Router MIB (MPLS-LSR-MIB) allows you to use the Simple Network Management Protocol (SNMP) to remotely monitor a label switch router (LSR) that is using the Multiprotocol Label Switching (MPLS) technology.
Scalability enhancements provided in the Cisco IOS 12.0(28)S release reduce the size of any MIB walk and improve the usability of the MPLS-LSR-MIB.
Note |
In Cisco IOS Release 12.2(33)SRB and Cisco IOS Release 12.2(33)SB, this MIB has been deprecated and replaced by MPLS-LSR-STD-MIB (RFC 3813). In those two releases and in later images, the entire MIB can be referenced by the name mplsLsrMIB for purposes of the SNMP server excluded/included command. If other MIB object names need to be referenced on the router, they must be referenced by MPLS-LSR-MIB::<table_entry_name>. |
Release |
Modification |
---|---|
12.0(14)ST |
This feature was introduced on Cisco IOS Release 12.0(14)ST |
12.2(2)T |
This feature was integrated into Cisco IOS Release 12.2(2)T. |
12.0(22)S |
This feature was implemented on the Cisco 12000 series routers and integrated into Cisco IOS Release 12.0(22)S. |
12.2(14)S |
This feature was integrated into Cisco IOS Release 12.2(14)S and implemented on Cisco 7200 and Cisco 7500 series routers. |
12.2(25)S |
This feature was updated to work in the MPLS High Availability environment with the Cisco 7500 series routers. |
12.0(28)S |
This feature was updated to include scalability enhancements in Cisco IOS Release 12.0(28)S. |
12.2(33)SRB |
This MIB has been deprecated and replaced by MPLS-LSR-STD-MIB (RFC 3813). |
12.2(33)SB |
This MIB has been deprecated and replaced by MPLS-LSR-STD-MIB (RFC 3813). |
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 Table at the end of this document.
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.
The MPLS-LSR-MIB contains managed objects that support the retrieval of label switching information from a router. The MIB is based on Revision 05 of the IETF MPLS-LSR-MIB. The MPLS-LSR-MIB mirrors a portion of the Cisco MPLS subsystem; specifically, it mirrors the Label Forwarding Information Base (LFIB). This implementation enables a network administrator to get information on the status, character, and performance of the following:
In addition, the network administrator can retrieve the status of cross-connect table entries that associate MPLS segments with each other.
The figure below shows the association of the cross-connect table with incoming and outgoing segments (labels).
Figure 1 | Label Forwarding with the Cross-Connect Table |
Note |
The out-segment table does not display "no label" entries. Labels that are displayed as "POP" are the special MPLS label 3. |
The notation used in the MPLS-LSR-MIB follows the conventions defined in Abstract Syntax Notation One (ASN.1). ASN.1 defines an Open System Interconnection (OSI) language used to describe data types apart from particular computer structures and presentation techniques. Each object in the MIB incorporates a DESCRIPTION field that includes an explanation of the object's meaning and usage, which, together with the other characteristics of the object (SYNTAX, MAX-ACCESS, and INDEX) provides sufficient information for management application development, as well as for documentation and testing.
The MPLS-LSR-MIB represents an ASN.1 notation reflecting an idealized MPLS LSR.
A network administrator can access the entries (objects) in the MPLS-LSR-MIB by means of any SNMP-based network management system (NMS). The network administrator can retrieve information in the MPLS-LSR-MIB using standard SNMP get and getnext operations.
Typically, SNMP runs as a low-priority process. The response time for the MPLS-LSR-MIB is expected to be similar to that for other MIBs. The size and structure of the MIB and other MIBs in the system influence response time when you retrieve information from the management database. Traffic through the LSR also affects SNMP performance. The busier the switch is with forwarding activities, the greater the possibility of lower SNMP performance.
The top-level components of the MPLS-LSR-MIB consist of
This Cisco implementation does not support the notifications defined in the MIB, nor does it support the labelStackTable or the trafficParamTable.
The Cisco implementation of the MPLS-LSR-MIB supports four main tables:
The MIB contains three supplementary tables to supply performance information. This implementation does not support the label stack and traffic parameter tables.
The following sections list the MPLS-LSR-MIB tables (main and supplementary), their functions, table objects that are supported, and table objects that are not supported.
Provides information for each MPLS-capable interface on an LSR.
Supports:
Does not support:
Augments the MPLS interface configuration table.
Supports:
Does not support:
Contains a description of incoming segments (labels) at an LSR and their associated parameters.
Administrative and operational status objects for this table control packet transmission. If administrative and operational status objects are down, the LSR does not forward packets. If these status objects are up, the LSR forwards packets.
Supports:
Note |
The administrative status and operational status are always up for inSegments in the Cisco implementation. Otherwise, these entries do not appear in the table. |
Does not support:
Augments the MPLS in-segment table, providing performance information and counters for incoming segments on an LSR.
Supports:
Note |
The lastFailure parameter is set to zero because it has no meaning in the Cisco implementation. |
Does not support:
Contains a description of outgoing segments from an LSR and their associated parameters.
Administrative and operational status objects for this table control packet transmission. If administrative and operational status objects are down, the LSR does not forward packets. If these values are up, the LSR forwards packets.
Supports:
Note |
The administrative and operational status entries are always up in the Cisco implementation. Otherwise, the administrative and operational status entries do not appear in the table. |
Does not support:
Augments the MPLS out-segment table, providing performance information and counters for outgoing segments on an LSR.
Supports:
Does not support:
Associates inSegments (labels) with outSegments (labels) to show the manager how the LSR is currently swapping these labels.
A row in this table consists of one cross-connect entry that is indexed by the cross-connect index, the interface index of the incoming segment, the incoming label, and the out-segment index.
The administrative and operational objects for this table control packet forwarding to and from a cross-connect entry (XCEntry). The administrative status and operational status are always up in the Cisco implementation. Otherwise, the LSR would not forward packets.
Supports:
Note |
The administrative status and operational status are always up in the Cisco implementation. Otherwise, these status entries do not appear in the table. |
Does not support:
The MPLS-LSR-MIB supports several scalar objects. In the Cisco implementation of the MIB, the following scalar objects are hard-coded to the value indicated and are read-only objects:
The following scalar objects do not contain information for the MPLS-LSR-MIB and are coded as false:
No trap information exists to support the MIB. Therefore, the following traps are not supported:
In the cross-connect table, cross-connect entries associate incoming segments and interfaces with outgoing segments and interfaces. The following objects index the cross-connect entry:
The figure below shows the links between the in-segment and the out-segment in the cross-connect table.
Figure 2 | Cross-Connect Table Links |
The table below shows the cross-connect table links you might see in the output from SNMP get operations on the MPLS-LSR-MIB objects that index a cross-connect entry. These objects include
Table 1 | MPLS LSR Output Showing Cross-Connect Table Links |
In-Segment Values |
Cross-Connect Entry |
Out-Segment Values |
---|---|---|
01, 1000 |
5002, 0, 1000, 0Linking Table Elements |
-- |
|
501, 0, 1000, 501 |
501 = Pop (topLabel), Eth 1/5 |
|
502, 0, 1000, 502 |
502 = Pop (topLabel), Eth, 1/1 |
Note |
The OutSegmentIndex object is not the label. The label can be retrieved from the mplsOutSegmentTopLabel object. |
The MPLS interface configuration table lists interfaces that support MPLS technology. An LSR creates an entry dynamically in this table for each MPLS-capable interface. An interface becomes MPLS-capable when MPLS is enabled on that interface. A non-zero index for an entry in this table points to the ifIndex for the corresponding interface entry in the MPLS-layer in the ifTable of the Interfaces Group MIB.
The ifTable contains information on each interface in the network. Its definition of an interface includes any sublayers of the internetwork layer of the interface. MPLS interfaces fit into this definition of an interface. Therefore, each MPLS-enabled interface is represented by an entry in the ifTable.
The interrelation of entries in the ifTable is defined by the interfaces stack group of the Interfaces Group MIB. The figure below shows how the stack table might appear for MPLS interfaces. The underlying layer refers to any interface that is defined for MPLS internetworking, for example, ATM, Frame Relay, or Ethernet.
Figure 3 | Interface Group MIB Stack Table for MPLS Interfaces |
Note |
Tunnel interfaces are included in the MPLS list for the current implementation. |
The incoming and outgoing packets include a reference to the interface index for the ifTable of the Interfaces Group MIB. The figure below shows the links between MPLS-LSR-MIB objects and the Interfaces Group MIB.
Figure 4 | MPLS-LSR-MIB and Interfaces Group MIB Links |
The MPLS-LSR-MIB enables you to display the contents of the MPLS Label Forwarding Information Base (LFIB). It gives you the same information that you can obtain using the CLI command show mpls forwarding-table.
However, the MPLS-LSR-MIB approach offers these advantages over the CLI command approach:
The following paragraphs describe the MPLS-LSR-MIB structure and show, through the use of an example, how the two approaches to the information display compare.
MIB structure is represented by a tree hierarchy. Branches along the tree have short text strings and integers to identify them. Text strings describe object names, and integers allow computer software to encode compact representations of the names.
The MPLS-LSR-MIB falls on the experimental branch of the Internet MIB hierarchy. The experimental branch of the Internet MIB hierarchy is represented by the object identifier 1.3.6.1.3. This branch can also be represented by its object name iso.org.dod.internet.experimental . The MPLS-LSR-MIB is identified by the object name mplsLsrMIB , which is denoted by the number 96. Therefore, objects in the MPLS-LSR-MIB can be identified in either of the following ways:
To display a MIB-variable , you enter an SNMP get command with an object identifier. Object identifiers are defined by the MPLS-LSR-MIB.
The figure below shows the position of the MPLS-LSR-MIB in the Internet MIB hierarchy.
Figure 5 | MPLS-LSR-MIB in the Internet MIB Hierarchy |
The MPLS LFIB is the component of the Cisco MPLS subsystem that contains management information for LSRs. You can access this management information by means of either of the following:
The following examples show how you can gather LSR management information using both methods.
A show mpls forwarding-table CLI command allows you to look at label forwarding information for a packet on a specific MPLS LSR.
Router# show mpls forwarding-table
Local Outgoing Prefix Bytes Tag Outgoing Next Hop
Tag Tag or VC or Tunnel Id Switched interface
19 Pop Tag 10.3.4.0/24 0 Et1/4 10.22.23.23
22 23 14.14.14.14/32 0 AT2/0.1 point2point
1/36 14.14.14.14/32 0 AT2/0.2 point2point
SNMP commands on MIB objects also allow you to look at the label forwarding information for a specific MPLS LSR.
You can do a walk-through of the MIB by running a command such as getmany -v2c public mplsLsrMIB on a network manager where getmany does repeated SNMP getnext operations to retrieve the contents of the MPLS-LSR-MIB.
mplsXCOperStatus.9729.0.19.9729 = up(1) mplsXCOperStatus.11265.0.22.11265 = up(1) mplsXCOperStatus.11266.0.22.11266 = up(1)
You can continue to scan the output of the getmany command for the following (from the MPLS out-segment table):
mplsOutSegmentTopLabel.9729 = 3 mplsOutSegmentTopLabel.11265 = 23 mplsOutSegmentTopLabel.11266 = 65572
Note |
65572 is 1/36 in label form (1 is the high-order 16 bits. 36 is the low-order 16 bits.) |
mplsOutSegmentIfIndex.9729 = 7 mplsOutSegmentIfIndex.11265 = 28 mplsOutSegmentIfIndex.11266 = 31
The benefits described in the following paragraphs are available to you with the MPLS-LSR-MIB.
By monitoring the cross-connect entries and the associated incoming and outgoing segments, you can see which labels are installed and how they are being swapped. Use the MPLS-LSR-MIB in place of the show mpls forwarding CLI command.
By monitoring interface and packet operations on an MPLS LSR, you can identify high- and low-traffic patterns, as well as traffic distributions.
By identifying potentially high-traffic areas, you can set up load sharing to improve network performance.
By comparing results from SNMP get commands and the show mpls forwarding CLI command, you can verify your LSR configuration.
By monitoring the cross-connect entries and the associated incoming segments and outgoing segments, you can determine the active LSPs.
The MPLS-LSR-MIB requires the following:
Note |
Additional capacity is not required for runtime dynamic random-access memory (DRAM). |
The SNMP agent for the MPLS-LSR-MIB is disabled by default. To enable the SNMP agent, perform the following steps:
To verify that the SNMP agent has been enabled, perform the following steps:
Step 1 | Access the router through a Telnet session: Example:
Prompt# telnet xxx.xxx.xxx.xxx
where xxx.xxx.xxx.xxx represents the IP address of the target device. |
Step 2 | Enter privileged mode: Example:
Router# enable
|
Step 3 | Display the running configuration and look for SNMP information: Example:
Router# show running-configuration
...
...
snmp-server community public RO
If you see any "snmp-server" statements, SNMP has been enabled on the router. |
The following example shows how to enable an SNMP agent.
configure terminal snmp-server community
In the following example, SNMPv1 and SNMPv2C are enabled. The configuration permits any SNMP manager to access all objects with read-only permissions using the community string public .
configure terminal snmp-server community public
In the following example, read-only access is allowed for all objects to members of access list 4 that specify the comaccess community string. No other SNMP managers have access to any objects.
configure terminal nmp-server community comaccess ro 4
Related Topic |
Document Title |
---|---|
Configuring SNMP using Cisco IOS software |
Standard |
Title |
---|---|
draft-ietf-mpls-lsr-mib-05.txt |
MPLS Label Switch Router Management Information Base Using SMIv2 |
draft-ietf-mpls-arch-07.txt |
Multiprocol Label Switching Architecture |
MIBs |
MIBs Link |
---|---|
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs |
Title |
---|---|
The LSR implementation supporting the MPLS-LSR-MIB is in full compliance with all provisions of Section 10 of RFC 2026. |
The Internet Standards Process |
Description |
Link |
---|---|
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This feature uses no new or modified commands.
cross-connect (XC) --An association of in-segments and incoming Multiprotocol Label Switching (MPLS) interfaces to out-segments and outgoing MPLS interfaces.
IETF --Internet Engineering Task Force. A task force (consisting of more that 80 working groups) that is developing standards for the Internet and the IP suite of protocols.
inSegment --A label on an incoming packet that is used to determine the forwarding of the packet.
Internet Engineering Task Force --See IETF.
label --A short, fixed length identifier that is used to determine the forwarding of a packet.
Label Distribution Protocol --See LDP.
label switched path --See LSP.
label switching --Describes the forwarding of IP (or other network layer) packets by a label swapping algorithm based on network layer routing algorithms. The forwarding of these packets uses the exact match algorithm and rewrites the label.
label switch router --See LSR.
LDP --Label Distribution Protocol. A standard protocol that operates between Multiprotocol Label Switching (MPLS)-enabled routers to negotiate the labels (addresses) used to forward packets. The Cisco proprietary version of this protocol is the Tag Distribution Protocol (TDP).
LSP --label switched path. A sequence of hops in which a packet travels from one router to another router by means of label switching mechanisms. A label switched path can be established dynamically, based on normal routing mechanisms, or through configuration.
LSR --label switch router. A device that forwards Multiprotocol Label Switching (MPLS) packets based on the value of a fixed-length label encapsulated in each packet.
Management Information Base --See MIB.
MIB --Management Information Base. A database of network management information that is used and maintained by a network management protocol such as Simple Network Management Protocol (SNMP). The value of a MIB object can be changed or retrieved by means of SNMP commands, usually through a network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.
MPLS --Multiprotocol Label Switching. A switching method that forwards IP traffic through use of a label. This label instructs the routers and the switches in the network where to forward the packets. The forwarding of MPLS packets is based on preestablished IP routing information.
MPLS interface --An interface on which Multiprotocol Label Switching (MPLS) traffic is enabled.
Multiprotocol Label Switching --See MPLS.
notification request --A message sent by a Simple Network Management Protocol (SNMP) agent to a network management station, console, or terminal, indicating that a significant event occurred. SNMP notification requests are more reliable than traps, because a notification request from an SNMP agent requires that the SNMP manager acknowledge receipt of the notification request. The manager replies with an SNMP response protocol data unit (PDU). If the manager does not receive a notification message from an SNMP agent, it does not send a response. If the sender (SNMP agent) never receives a response, the notification request can be sent again.
outSegmen t--A label on an outgoing packet.
Simple Network Management Protocol --See SNMP.
SNMP --Simple Network Management Protocol. A management protocol used almost exclusively in TCP/IP networks. SNMP provides a means for monitoring and controlling network devices, and for managing configurations, statistics collection, performance, and security.
trap --A message sent by a Simple Network Management Protocol (SNMP) agent to a network management station, console, or terminal, indicating that a significant event occurred. Traps are less reliable than notification requests, because the receiver does not send an acknowledgment when it receives a trap. The sender cannot determine if the trap was received.
Note |
Refer to the Cisco Dictionary of Internetworking Terms and Acronyms for terms not included in this glossary. |
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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.