23.1.8 Databases Used by CFM

The following table describes the databases used by the CFM functionality.

Table 23-12: Databases Used by CFM
Database	Description	Command for checking its contents
MEP CCM database	A database maintained by each MEP. Information about MEPs in the same MA. The CC functionality uses this database when it monitors pervasive connectivity. The database holds the following information: MEP ID MAC addresses corresponding to the MEP ID Information about failures occurring at the applicable MEP.	show cfm remote-mep
MIP CCM database	A database maintained by switches. Information about MEPs in the same MA. This database is used to determine the port used for forwarding a linktrace message. The database holds the following information: MEP MAC address VLAN and the port on which CCMs of the applicable MEP were received	No
Linktrace database	A database holding the execution results of the linktrace functionality. The database holds the following information: The MEPs and the destinations where the linktrace functionality was executed TTL Information about switches that sent back responses Information about ports on which linktrace messages were received Information about ports from which linktrace messages were forwarded	show cfm l2traceroute-db

<Structure of this section>

(1) MEP CCM data base

The MEP CCM database holds information about the types of MEPs that are in the same MA. It also holds information about the failures occurring at the applicable MEPs.

Although you can specify the destination by using the MEP ID for the loopback functionality and the linktrace functionality, the MEP ID that are not registered in the MEP CCM database cannot be specified. You can use the show cfm remote-mep operation command to check if a MEP ID is registered in the database.

An entry in this database is created when a MEP receives a CCM while the CC functionality is running.

(2) MIP CCM data base

The MIP CCM database is used to determine the port from which a linktrace message was forwarded.

When a linktrace message is forwarded, if the MAC address of the destination MEP is not registered in the MIP CCM database, see the MAC address table to determine the port used to forward the message.

If the MAC address is not found in the MAC address table, a response indicating that the message could not be forwarded is sent to the source without forwarding the linktrace message.

An entry for this database is created when a MIP transfers a CCM while the CC functionality is running.

(3) Linktrace database

The linktrace database holds the execution results of the linktrace functionality.

You can use the show cfm l2traceroute-db operation command to see the results of executing the linktrace functionality in the past.

(a) Number of routes that can be retained

A switch can retain responses for a maximum of 1024 switches.

The number of routes that can be retained is determined by the number of switches per route. If you want to retain responses for 256 switches per route, you can have four routes. If you want to retain responses for 16 switches per route, you can have 64 routes.

If the number of responses exceeds for the number of responses allowed for 1024 switches, information about an old route is deleted, and information about the new route is saved.

When the linktrace functionality is executed at a destination that is registered in the linktrace database, the routing information from the linktrace database to the applicable destination is deleted first, and then the new linktrace response is saved.

The following figures show entries in the linktrace database.

Figure 23-30: Linktrace database

An entry in this database is created when a MEP receives a response while the linktrace functionality is running.