Brocade Multi-Service IronWare Administration Guide (Supporting R05.6.00) - Manual (Page 167)

Multi-Service IronWare Administration Guide 149
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Configuring IEEE 802.1ag CFM
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Each MP along the path returns a unicast Linktrace Reply back to the originating MEP. The MEP
sends a single LTM to the next hop along the trace path; however, it can receive many Linktrace
Responses from different MPs along the trace path and the destination MEP as the result of the
message traversing hop by hop. As mentioned previously, the age-out of MAC addresses can lead
to erasure of information at MIPs, where this information is used for the Linktrace mechanism.
Possible ways to address this behavior include:
• Carrying out Linktrace following fault detection or verification such that it gets exercised within
the window of age-out.
• Maintaining information about the destination MEP at the MIPs along the path using CCMs.
• Maintaining visibility of path at the source MEPs through periodic LTMs
Linktrace may also be used when no faults are apparent in order to discover the routes normally
taken by data through the network. In the rare instances during network malfunctions where
Linktrace cannot provide the information needed to isolate a fault, issuing Loopback Messages to
MPs along the normal data path may provide additional useful information.
The Linktrace message is used by one MEP to trace the path to another MEP or MIP in the same
domain. It is needed for Loopback (Ping). All intermediate MIPs respond back with a Link trace
reply to the originating MEP. After decreasing the TTL by one, intermediate MIPs forward the Link
trace message until the destination MIP or MEP is reached. If the destination is a MEP, every MIP
along a given MA responds to the originating MEP. The originating MEP can then determine the
MAC address of all MIPs along the MA and their precise location with respect to the originating
MEP.
Configuring IEEE 802.1ag CFM
Enabling or disabling CFM
To enable or disable the CFM protocol globally on the devices and enter into the CFM Protocol
Configuration mode, enter a command such as the following.
Brocade(config)#cfm-enable
Brocade(config-cfm)#
Syntax: [no] cfm-enable
The no form of the command disables the CFM protocol.
Creating a Maintenance Domain
A Maintenance Domain is the network or the part of the network for which faults in connectivity are
to be managed. A Maintenance Domain consists of a set of Domain Service Access Points.
A Maintenance Domain is, or is intended to be, fully connected internally. A Domain Service Access
Point associated with a Maintenance Domain has connectivity to every other Domain Service
Access Point in the Maintenance Domain, in the absence of faults.
Each Maintenance Domain can be separately administered.
The domain-name command in CFM protocol configuration mode creates a maintenance domain
with a specified level and name and enters the Specific Maintenance Domain mode specified in
the command argument.