Cisco Systems A9014CFD manual Setting Up and Configuring Ethernet OAM, 10-35

Chapter 10 Configuring Ethernet OAM

When an interface is set to the remote loopback mode the interface no longer participates in any other Layer 2 or Layer 3 protocols; for example Spanning Tree Protocol (STP) or Open Shortest Path First (OSPF). The reason is that when two connected ports are in a loopback session, no frames other than the OAM PDUs are sent to the CPU for software processing. The non-OAM PDU frames are either looped back at the MAC level or discarded at the MAC level.

From a user's perspective, an interface in loopback mode is in a link-up state.

Cisco Vendor-Specific Extensions

Ethernet OAM allows vendors to extend the protocol by allowing them to create their own type-length-value (TLV) fields.

OAM Messages

Ethernet OAM messages or OAM PDUs are standard length, untagged Ethernet frames within the normal frame length bounds of 64 to 1518 bytes. The maximum OAM PDU frame size exchanged between two peers is negotiated during the discovery phase.

OAM PDUs always have the destination address of slow protocols (0180.c200.0002) and an Ethertype of 8809. OAM PDUs do not go beyond a single hop and have a hard-set maximum transmission rate of 10 OAM PDUs per second. Some OAM PDU types may be transmitted multiple times to increase the likelihood that they will be successfully received on a deteriorating link.

Four types of OAM messages are supported:

•Information OAM PDU—A variable-length OAM PDU that is used for discovery. This OAM PDU includes local, remote, and organization-specific information.

•Event notification OAM PDU—A variable-length OAM PDU that is used for link monitoring. This type of OAM PDU may be transmitted multiple times to increase the chance of a successful receipt; for example, in the case of high-bit errors. Event notification OAM PDUs also may include a time stamp when generated.

•Loopback control OAM PDU—An OAM PDU fixed at 64 bytes in length that is used to enable or disable the remote loopback command.

•Vendor-specific OAM PDU—A variable-length OAM PDU that allows the addition of vendor-specific extensions to OAM.

For instructions on how to configure Ethernet Link OAM, see Setting Up and Configuring Ethernet OAM, page 10-35.

Setting Up and Configuring Ethernet OAM

This section includes the following topics:

•Default Ethernet OAM Configuration, page 10-36

•Restrictions and Guidelines, page 10-36

•Enabling Ethernet OAM on an Interface, page 10-36

•Enabling Ethernet OAM Remote Loopback, page 10-38

•Configuring Ethernet OAM Link Monitoring, page 10-38

•Configuring Ethernet OAM Remote Failure Indications, page 10-41

•Configuring Ethernet OAM Templates, page 10-42

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09		10-35