Users Guide

802.1ag
Ethernet operations, administration, and maintenance (OAM) are a set of tools used to install, monitor, troubleshoot, and manage Ethernet
infrastructure deployments. Ethernet OAM consists of three main areas:
• Service layer OAM — IEEE 802.1ag connectivity fault management (CFM)
• Link layer OAM — IEEE 802.3ah OAM
• Ethernet local management Interface — (MEF-16 E-LMI)
Topics:
• Ethernet CFM
• Maintenance Domains
• Maintenance Points
• Maintenance End Points
• Implementation Information
• Configuring the CFM
• Enable Ethernet CFM
• Creating a Maintenance Domain
• Creating a Maintenance Association
• Create Maintenance Points
• Continuity Check Messages
• Sending Loopback Messages and Responses
• Sending Linktrace Messages and Responses
• Enabling CFM SNMP Traps
• Displaying Ethernet CFM Statistics
Ethernet CFM
Ethernet CFM is an end-to-end per-service-instance Ethernet OAM scheme which enables: proactive connectivity monitoring, fault
verification, and fault isolation.
The service-instance with regard to OAM for Metro/Carrier Ethernet is a virtual local area network (VLAN). This service is sold to an end-
customer by a network service provider. Typically the service provider contracts with multiple network operators to provide end-to-end
service between customers. For end-to-end service between customer switches, connectivity must be present across the service
provider through multiple network operators.
Layer 2 Ethernet networks usually cannot be managed with IP tools such as internet control message protocol (ICMP) Ping and IP
Traceroute. Traditional IP tools often fail because:
• there are complex interactions between various Layer 2 and Layer 3 protocols such as spanning tree protocol (STP), link aggregation
group (LAG), virtual router redundancy protocol (VRRP), and electronic commerce messaging protocol (ECMP) configurations.
• ping and traceroute are not designed to verify data connectivity in the network and within each node in the network (such as in the
switching fabric and hardware forwarding tables).
• when networks are built from different operational domains, access controls impose restrictions that cannot be overcome at the IP
level, resulting in poor fault visibility. There is a need for hierarchical domains that can be monitored and maintained independently by
each provider or operator.
• routing protocols choose a subset of the total network topology for forwarding, making it hard to detect faults in links and nodes that
are not included in the active routing topology. This is made more complex when using some form of traffic engineering (TE) based
routing.
• network and element discovery and cataloging is not clearly defined using IP troubleshooting tools.
There is a need for Layer 2 equivalents to manage and troubleshoot native Layer 2 Ethernet networks. With these tools, you can identify,
isolate, and repair faults quickly and easily, which reduces operational cost of running the network. OAM also increases availability and
reduces mean time to recovery, which allows for tighter service level agreements, resulting in increased revenue for the service provider.
In addition to providing end-to-end OAM in native Layer 2 Ethernet Service Provider/Metro networks, you can also use CFM to manage
and troubleshoot any Layer 2 network including enterprise, datacenter, and cluster networks.
5
70 802.1ag