CISCO-GPRS-L2RLY-MIB

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Organization: Cisco Systems, Inc.

Last Updated: 1998-12-15

Category: Cisco Devices, Mobile IP, Telephony and VoIP

Description: Provides management objects for monitoring the GPRS Layer 2 relay function on Cisco mobile data network equipment.

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What Is CISCO-GPRS-L2RLY-MIB?

CISCO-GPRS-L2RLY-MIB is a Cisco-specific module for managing the Layer 2 Relay (L2RLY) function used inside a split-architecture Serving GPRS Support Node (SGSN) in Cisco/Alcatel joint GPRS mobile-network deployments. In this architecture the SGSN is divided into a Telecom node (T-node) and a Datacom node (D-node) connected by dual fast-Ethernet links, and L2RLY is the lightweight connectionless protocol that forwards packets between them. The MIB exposes configuration data (unit types, echo timers, flow-control flags) and per-interface tables that let an operator monitor the health and software/communication status of this link, including keepalive responsiveness, flow-control trigger events, and dropped-packet counts that reveal congestion or a failed peer. It works alongside general SNMP interface conventions and Cisco's GPRS MIB family rather than a formal IETF standard, since it was created for a proprietary joint-development architecture. It is deployed exclusively on Cisco/Alcatel SGSN equipment in 2G/2.5G mobile packet-core networks, largely in legacy GPRS installations. Engineers can download the CISCO-GPRS-L2RLY-MIB file directly to load it into their MIB browser.

IPNetwork Monitor allows you to monitor SNMP objects defined in CISCO-GPRS-L2RLY-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/Alcatel split-architecture SGSN (GPRS mobile core node)

Monitoring Examples

An operator would poll cgprsL2rlyInterfaceTable/cgprsL2rlyInterfaceEntry, keyed by cgprsL2rlyInterfaceId, to check cgprsL2rlyInterfaceRowStatus and confirm each T-node/D-node link is active. A rising cgprsL2rlyDroppedPktsMonTime count or repeated cgprsL2rlyFlowControlTriggerCount events would indicate the fast-Ethernet link between nodes is congested or unstable. Enabling cgprsL2rlyNoRespToKeepAliveMsgNotificationEnable and cgprsL2rlyUnitJoinNotificationEnable lets the SGSN emit traps when a D-node stops answering keepalives or when a unit newly joins, giving early warning of a partial node failure.

What Can Be Monitored

L2RLY interface status
keepalive/echo responsiveness
flow control trigger events
dropped packet counts
unit join/leave events
SGSN node connectivity

Imported Objects

From CISCO-SMI

ciscoMgmt

OBJECT-IDENTITY

From IF-MIB

InterfaceIndex

From SNMPv2-CONF

MODULE-COMPLIANCE
OBJECT-GROUP

From SNMPv2-SMI

Counter32
Integer32
MODULE-IDENTITY
NOTIFICATION-TYPE
OBJECT-TYPE

From SNMPv2-TC

RowStatus
TruthValue

How to Use in IPNetwork Monitor

Example using cgprsL2rlyFlowControlTriggerCount OID:

Select a Cisco/Alcatel split-architecture SGSN (GPRS mobile core node) 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 cgprsL2rlyFlowControlTriggerCount into the Find box to locate it in the OID tree, then select it and click OK. It reports a running count indicating how many times L2 Relay flow control has been trigerred. 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 Counter32-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, 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
ciscoGprsL2rlyMIB	1.3.6.1.4.1.9.9.9993			The MIB Module for managing the General Packet Radio Service(GPRS) L2RLY related information on Servicing GPRS Support Node(SGSN). In GPRS network, a SGSN is typically implemented as a single node; in cisco-Alcatel joint development, it's split into Telecom part (T-node) and Datacom part (D-node). T-nodes and D-nodes are connected by two fast ethernets. A simple connectionless protocol called L2RLY is used to provide service of forwarding packet between T-unit and D-unit, flow control and defending against the failure of a FE subnet.
ciscoGprsL2rlyObjects	1.3.6.1.4.1.9.9.9993.1
ciscoGprsL2rlyConfig	1.3.6.1.4.1.9.9.9993.1.1
I32 cgprsL2rlyUid	1.3.6.1.4.1.9.9.9993.1.1.1	Integer32	read-write	L2 Relay unit identification.
INT cgprsL2rlyUnitType	1.3.6.1.4.1.9.9.9993.1.1.2	INTEGER	read-write	The type can be either a datacom unit, or a telecom unit.
I32 cgprsL2rlyEchoTimer	1.3.6.1.4.1.9.9.9993.1.1.3	Integer32	read-write	The frequency of transmission of self_id packet. This packet is transmitted periodically, for keep-alive and auto discovery purposes.
T/F cgprsL2rlyFlowControlFlag	1.3.6.1.4.1.9.9.9993.1.1.4	TruthValue	read-write	L2 Relay flow control function flag. 'on' means that the flow control has been enabled, and 'off' means the converse.
I32 cgprsL2rlyDroppedPktsMonTime	1.3.6.1.4.1.9.9.9993.1.1.5	Integer32	read-write	The configurable time duration for monitoring the excessive rate at which packets are dropped by the L2 Relay on SGSN due to traffic congestion problem.
T/F cgprsL2rlyNoRespToKeepAliveMsgNotificationEnable	1.3.6.1.4.1.9.9.9993.1.1.6	TruthValue	read-write	The object indicates whether the system produces the cgprsL2rlyNoRespToKeepAliveMsgNotification. A false value will prevent the cgprsL2rlyNoRespToKeepAliveMsgNotification from being generated by this system.
T/F cgprsL2rlyUnitJoinNotificationEnable	1.3.6.1.4.1.9.9.9993.1.1.7	TruthValue	read-write	The object indicates whether the system produces the cgprsL2rlyUnitJoinNotification. A false value will prevent the cgprsL2rlyUnitJoinNotificationcgprs from being generated by this system.
cgprsL2rlyInterfaceTable	1.3.6.1.4.1.9.9.9993.1.1.8		not-accessible	The table that lists the interfaces which l2rly is using. Currently the table has just two and always two entries. There is only one l2rly T or D unit on each router. To ensure reliability and do load sharing, there could be two fast ethernets among the l2rly units. Thus each l2rly unit could interface with two fast ethernets. At least one interface should be configured and working in order for l2rly to work.
cgprsL2rlyInterfaceEntry	1.3.6.1.4.1.9.9.9993.1.1.8.1		not-accessible	The l2rly interface table entry.
NUM cgprsL2rlyInterfaceId	1.3.6.1.4.1.9.9.9993.1.1.8.1.1	InterfaceIndex	not-accessible	The ifIndex for the corresponding interface which l2rly is using.
ROW cgprsL2rlyInterfaceRowStatus	1.3.6.1.4.1.9.9.9993.1.1.8.1.2	RowStatus	read-create	The status for row creation and deletion.
ciscoGprsL2rlyStats	1.3.6.1.4.1.9.9.9993.1.2
C32 cgprsL2rlyFlowControlTriggerCountEx	1.3.6.1.4.1.9.9.9993.1.2.1	Counter32	read-only	A running count indicating how many times L2 Relay flow control has been trigerred.
C32 cgprsL2rlyInputQLen	1.3.6.1.4.1.9.9.9993.1.2.2	Counter32	read-only	The L2 Relay input queue length.
C32 cgprsL2rlyTotalPacketsDropped	1.3.6.1.4.1.9.9.9993.1.2.3	Counter32	read-only	Total number of packets dropped by L2 Relay due to unknown headers since system startup.
I32 cgprsL2rlyDroppedPktsTimeFrame	1.3.6.1.4.1.9.9.9993.1.2.4	Integer32	read-only	The time frame within which the number of L2 Relay packets, defined by cgprsL2rlyDroppedPktsCount, are dropped.
C32 cgprsL2rlyDroppedPktsCount	1.3.6.1.4.1.9.9.9993.1.2.5	Counter32	read-only	The number of packets dropped by L2 Relay on the SGSN within cgprsL2rlyDroppedPktsTimeFrame.
cgprsL2rlyPeerTable	1.3.6.1.4.1.9.9.9993.1.2.6		not-accessible	The table lists all the l2rly units on the peer nodes that directly connect with this l2rly units through two fast ethernets.
cgprsL2rlyPeerEntry	1.3.6.1.4.1.9.9.9993.1.2.6.1		not-accessible	L2rly unit peer entries.
I32 cgprsL2rlyPeerUid	1.3.6.1.4.1.9.9.9993.1.2.6.1.1	Integer32	not-accessible	The Uid that uniquely identify the peer l2rly unit that connects to the same fast ethernets as this l2rly unit.
INT cgprsL2rlyPeerUnitType	1.3.6.1.4.1.9.9.9993.1.2.6.1.2	INTEGER	read-only	The type of the peer l2rly on other devices which connects to the same fast ethernets as this one.
ciscoGprsL2rlyNotificationPrefix	1.3.6.1.4.1.9.9.9993.2
ciscoGprsL2rlyNotifications	1.3.6.1.4.1.9.9.9993.2.0
NTF cgprsL2rlyUnitJoinNotification	1.3.6.1.4.1.9.9.9993.2.0.1			This trap indicates that a new 'SGSN T-node' joins the service. This happens when a new SGSN node restarts or the network problem (fast ethernets among the units) recovers.
NTF cgprsL2rlyNoRespToKeepAliveMsgNotification	1.3.6.1.4.1.9.9.9993.2.0.2			This trap indicates that the 'SGSN T-node' failed to respond to the L2 Relay 'Keep Alive' message. The cgprsL2rlyUid variable identifies the 'SGSN T-node' that failed to respond.
ciscoGprsL2rlyConformances	1.3.6.1.4.1.9.9.9993.3
cgprsL2rlyCompliances	1.3.6.1.4.1.9.9.9993.3.1
cgprsL2rlyCompliance	1.3.6.1.4.1.9.9.9993.3.1.1			The compliance statement for entities which implement the CISCO GPRS L2RLY MIB.
cgprsL2rlyGroups	1.3.6.1.4.1.9.9.9993.3.2
cgprsL2rlyConfigGroup	1.3.6.1.4.1.9.9.9993.3.2.1			A collection of configurable parameters for L2RLY.
cgprsL2rlyStatsGroup	1.3.6.1.4.1.9.9.9993.3.2.2			A collection of stats for L2RLY.

RFC description

GPRS L2RLY relay protocol management for connectionless packet forwarding in SGSN nodes.

Start monitoring Cisco/Alcatel split-architecture SGSN (GPRS mobile core node) 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-GPRS-L2RLY-MIB