Cisco ASR 920 series, Руководство по настройке Ethernet-маршрутизатора

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Cross-Check Traps
•
Service up
—
Sent when all expected remote MEPs are up in time.
• MEP missing — Sent when an expected MEP is down.
• Unknown MEP — Sent when a CCM is received from an unexpected MEP.
Ethernet CFM and Ethernet OAM Interaction
To understand how CFM and OAM interact, you should understand the following concepts:
Ethernet Virtual Circuit
An EVC as defined by the Metro Ethernet Forum is a port-level point-to-point or multipoint-to-multipoint
Layer 2 circuit. EVC status can be used by a CE device either to find an alternative path in to the service
provider network or in some cases, to fall back to a backup path over Ethernet or over another alternative
service such as ATM.
OAM Manager
The OAM manager is an infrastructure element that streamlines interaction between OAM protocols. The
OAM manager requires two interworking OAM protocols, in this case Ethernet CFM and Ethernet OAM.
Interaction is unidirectional from the OAM manager to the CFM protocol and the only information exchanged
is the user network interface (UNI) port status. Additional port status values available include
•
REMOTE_EE
—
Remote excessive errors
•
LOCAL_EE
—
Local excessive errors
• TEST — Either remote or local loopback
After CFM receives the port status, it communicates that status across the CFM domain.
CFM over Bridge Domains
Connectivity Fault Management (CFM) over bridge domains allows untagged CFM packets to be associated
with a maintenance end point (MEP). An incoming untagged customer CFM packet has an EtherType of CFM
and is mapped to an Ethernet virtual circuit (EVC) or bridge domain based on the encapsulation configured
on the Ethernet flow point (EFP). The EFP is configured specifically to recognize these untagged packets.
An EFP is a logical demarcation point of an EVC on an interface and can be associated with a bridge domain.
The VLAN ID is used to match and map traffic to the EFP. VLAN IDs have local significance per port similar
to an ATM virtual circuit. CFM is supported on a bridge domain associated with an EFP. The association
between the bridge domain and the EFP allows CFM to use the encapsulation on the EFP. All EFPs in the
same bridge domain form a broadcast domain. The bridge domain ID determines the broadcast domain.
The distinction between a VLAN port and the EFP is the encapsulation. VLAN ports use a default dot1q
encapsulation. For EFPs, untagged, single tagged, and double tagged encapsulation exists with dot1q and
IEEE dot1ad EtherTypes. Different EFPs belonging to the same bridge domain can use different encapsulations.
Carrier Ethernet Configuration Guide (Cisco ASR 920 Series)
133
Configuring Ethernet Connectivity Fault Management in a Service Provider Network
Ethernet CFM and Ethernet OAM Interaction