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:
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 10.29.4.2 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 10.29.4.2 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:
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 10.29.4.2 cfrExtCircuitIfName cfrExtCircuitIfName.2.101 : Serial0.1 cfrExtCircuitIfName.2.201 : Serial0.2 cfrExtCircuitIfName.2.301 : Serial0.3 cfrExtCircuitIfName.2.401 : Serial0.4 > snmpwalk 10.29.4.2 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.
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.