Brocade Communications Systems Brocate Ethernet Access Switch 6910 User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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Connectivity Fault Management
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Basic CFM Operations
CFM uses standard Ethernet frames for sending protocol messages. Both the source and
destination address for these messages are based on unicast or multicast MAC addresses, and
therefore confined to a single Layer 2 CFM service VLAN. For this reason, the transmission,
forwarding, and processing of CFM frames is performed by bridges, not routers. Bridges that do not
recognize CFM messages forward them as normal data. There are three basic types of CFM
messages, including continuity check, link trace, and loop back.
Continuity check messages (CCMs) are multicast within a single Service Instance (i.e., a specific
MA), allowing MEPs to discover other MEPs within the same MA, and MIPs to discover MEPs.
Connectivity faults are indicated when a known MEP stops sending CCMs, or a remote MEP
configured in a static list does not come up. Configuration errors, such as a cross-connect between
different MAs, are indicated when a CCM is received with an incorrect MA identifier or maintenance
level.
Loop back messages are used for fault verification. These messages can be sent using the MAC
address of any destination MEP within the same MA. If the target MEP’s identifier has been
discovered through CCM messages, then a loop back message can also be sent using the MEPs
identifier. A reply indicates that the destination is reachable.
Link trace messages are used for fault verification. These messages are multicast frames sent out
to track the hop-by-hop path to a target MEP within the same MA. Responses provide information
on the ingress, egress, and relay action taken at each hop along the path, providing vital
information about connectivity problems. Responses allow the sender to discover all of the
maintenance points that would be traversed by a data frame sent to the target MAC address.
SNMP traps can also be configured to provide an automated method of fault notification. If the
fault notification generator detects one or more defects within the configured time period, and fault
alarms are enabled, a corresponding trap will be sent. No further fault alarms are sent until the
fault notification generator has been reset by the passage of a configured time period without
detecting any further faults. Upon receiving a fault alarm, you should inspect the related SNMP
objects for the reporting MEP, diagnose the fault, correct it, and re-examine the MEP’s SNMP
objects to see whether the fault notification generator has been reset.
Configuration Guidelines
1. Configure the maintenance domains with the MD List (see
2. Configure the maintenance associations with MA List (see
3. Configure the local maintenance end points (MEPs) which will serve as the domain service
access points for the specified maintenance association using the MEP List (see
4. Enter a static list of MEPs assigned to other devices within the same maintenance association
using the Remote MEP List (see
"Configuring Remote Maintenance End Points"
). This allows
CFM to automatically verify the functionality of these remote end points by cross-checking the
static list configured on this device against information learned through continuity check
messages.
5. Enable CFM globally on the switch using the Configure Global screen (see
6. Enable CFM on the local MEPs using the Configure Interface screen (see
).