Configuring the OAM F4 Cell Flows
For ATM2 IQ interfaces, the F4 flow cell is used for management of the VP level. If your router is equipped with an ATM2 IQ PIC, you can configure OAM F4 cell flows to identify and report VPC defects and failures. The Junos OS supports three types of OAM F4 cells in end-to-end F4 flows:
Virtual Path Alarm Indication Signal (VP-AIS)
Virtual Path Remote Defect Indication (VP-RDI)
Virtual Path Loopback
The Junos OS does not support segment F4 flows, VPC continuity check, or VP performance management functions.
On each VP, you can configure an interval during which to transmit loopback cells by including the oam-period statement at the [edit interfaces interface-name atm-options vpi vpi-identifier] hierarchy level:
When you add a VPI at the atm-options hierarchy, an end-to-end F4 VCI is automatically opened to send and receive OAM F4, VP-AIS, and VP-RDI cells. If you enable OAM by including the oam-period statement in the configuration, the router sends and receives OAM F4 loopback cells.
If the physical ATM interface is configured with encapsulation type atm-ccc-cell-relay, then F4 VCIs are not created, and F4 OAM processing is not performed for the VPIs configured on that interface.
To modify OAM liveness values on a VP, include the oam-liveness statement at the [edit interfaces interface-name atm-options vpi vpi-identifier] hierarchy level:
up-count is the minimum number of consecutive OAM F4 loopback cells received on a VPI before it is declared up.
down-count is the minimum number of consecutive OAM F4 loopback cells lost before a VPI is declared down.
When a VP-AIS or VP-RDI cell is received, the VPI is marked down. When a VP-AIS cell is received on a VPI, a VP-RDI is generated and transmitted on the same VPI. When an OAM F4 loopback request cell is received, the router sends a loopback reply cell, even if the oam-period statement is not included in the configuration of the VPI.
When a VPI is marked down because the VPI receives VP-AIS, VP-RDI, VC-AIS, or VC-RDI cells, or because the VPI does not receive down-count consecutive OAM F4 loopback replies, all the VCIs that belong to the VPI are marked down. When a VPI is marked up, all the VCIs that belong to the VPI are marked up. The status of logical interfaces is also changed when the status of the last VCI on that interface is changed.
For a configuration example, see Example: Configuring ATM2 IQ Interfaces.
For interfaces that are configured for cell-relay promiscuous virtual path identifier (VPI) mode, the show interfaces command output does not show (OAM) F4 cell statistics.