Identifying Frame Relay Interfaces

Before going into either performance or fault management for Frame Relay, you need to be able to associate the physical interface, sub-interface, and PVC. This section discusses steps for finding out whether Frame Relay is set up on a serial port. The process discussed should reveal the following information for a Cisco router:

  • Number of interfaces

  • Types of interfaces

  • Whether Frame Relay is configured

  • Sub-interface and DLCI numbers using the cfrExtCircuitTable

  • Statistics from the frCircuitTable (RFC 1315)

The variables used to gather this data are not covered in detail here, but are shown as examples of what you would need to gather to effectively map the router interfaces to the appropriate DLCIs. (The ifTable objects shown in the next example were covered in more detail in Chapter 12, "Monitoring System Interfaces.")

Identifing Frame Relay Interfaces

To examine the serial ports to find if any are configured for Frame Relay, use the ifName and ifType variables from the ifTable:

 > snmpwalk ifName ifName.1 : Et0 ifName.2 : Se0 ifName.3 : Se1 ifName.4 : Nu0 ifName.5 : Lo0 ifName.6 : Lo253 ifName.7 : Se0.1 ifName.8 : Se0.2 ifName.9 : Se0.3 ifName.10 : Se0.4 > snmpwalk ifType ifType.1 : ethernetCsmacd ifType.2 : frameRelay ifType.3 : propPointToPointSerial ifType.4 : other ifType.5 : softwareLoopback ifType.6 : softwareLoopback ifType.7 : frameRelay ifType.8 : frameRelay ifType.9 : frameRelay ifType.10 : frameRelay 

Now you know that the first serial port 0 and its sub-interfaces are Frame Relay.

Using the Cisco Frame-Relay MIB to Identify the Sub-interface

Identifying the sub-interface and associated DLCIs is essential for starting the data collection for either performance or fault management. At this point, you will need to use the Cisco Frame-Relay MIB's cfrExtCircuitTable; specifically, the following variables:

  • cfrExtCircuitIfName DisplayString: The text name of the interface or sub-interface with the associated DLCI. This is the same name string of an interface used in the configuration and all console displays, such as 'serial 0', 'serial 3/0.3', for instance: ciscoMgmt. = Serial1.3, where the OID is the cfrExtCircuitIfName.

  • cfrExtCircuitIfType INTEGER: The type of the sub-interface this DLCI is associated with, if configured mainInterface(1), pointToPoint(2), multipoint(3). For instance, ciscoMgmt. = 3 would indicate as the cfrExtCircuitIfType, 5 is the main interface from the frCircuitIfIndex, 20 is the DLCI, and this sub-interface is configured for multipoint.

  • cfrExtCircuitSubifIndex InterfaceIndex: For a value greater than 0, this variable indicates the network management interface index for the sub-interface associated with this DLCI. Value 0 means the DLCI is not associated with any sub-interface. For example, ciscoMgmt.cfrExtCircuitSubifIndex.2.201 = 7 would indicate that the ifIndex for this sub-interface is 7.

The cfrExtCircuitTable is indexed by frCircuitIfIndex, frCircuitDlci. It provides the ifIndex value of the ifEntry this virtual circuit is layered onto and the DLCI for this virtual circuit. In the following example, the indexed number is 2, with the DLCI number following:

 > snmpwalk cfrExtCircuitIfName cfrExtCircuitIfName.2.101 : Serial0.1 cfrExtCircuitIfName.2.201 : Serial0.2 cfrExtCircuitIfName.2.301 : Serial0.3 cfrExtCircuitIfName.2.401 : Serial0.4 > snmpwalk cfrExtCircuitIfType cfrExtCircuitIfType.2.101 : pointToPoint cfrExtCircuitIfType.2.201 : multipoint cfrExtCircuitIfType.2.301 : multipoint cfrExtCircuitIfType.2.401 : multipoint 

From the data gathered in this example, you can build a table such as Table 16-1.

Table 16-1. Correlating Interfaces, Sub-interfaces, and Virtual Circuits
ifIndex Namestring Subiftype DLCIs
7 Serial0.1 PointToPoint 101
8 Serial0.2 Multipoint 201
9 Serial0.3 Multipoint 301
10 Serial0.4 Multipoint 401

This gives you the basic information needed to correlate the performance and fault data in the chapter to the interface or sub-interface and the virtual circuits.

Performance and Fault Management
Performance and Fault Management: A Practical Guide to Effectively Managing Cisco Network Devices (Cisco Press Core Series)
ISBN: 1578701805
EAN: 2147483647
Year: 2005
Pages: 200

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