7-2 FRX4000/FRX6000 4.0 User Guide, Rev 01DLCI SharingEach logical connection on a physical frame relay port is assigned a Data Link Con-nection Identifier (DLCI), which identifies a point-to-point connection, as shown inthe following example. (The numbers represent DLCIs.)Multiple protocols can be passed over a single physical frame relay port by sharing aDLCI. Each node supports up to 976 user-configurable DLCIs. (Several more are sup-ported, but are reserved for internal use.)Frame Relay BackupFrame relay virtual-circuit backup in the FRX4000/FRX6000 provides frame relayDLCIs with automatic backup protection in the event of LMI loss or port failure. (ADLCI is considered down/inactive if level 1 is down. If LMI is used, the DLCI is alsoconsidered inactive if not reported as active in a Full Status Message from the DCE.)A physical frame relay port can be dedicated to providing backup DLCIs, or backupscan co-exist with "regular" DLCIs on a port.In a backup configuration, one end is considered the "initiating" node and the other the"remote" node. The initiating end is the one that will establish the backup link if it dis-covers that the primary link is down. (A node can be the initiating node for somebackup configurations and the remote node for others.)Any sessions in progress when a primary DLCI goes down will not betransferred directly to the backup DLCI, but will be reset, then establishedon the backup.DLCIs used for backup on the initiating node are assigned to "backup groups," eachof which can contain up to ten backup DLCIs. A backup group is then assigned to oneor more "primary" DLCIs (the ones that will be backed up).The basic procedure for configuring backup DLCIs is:1. Configure all DLCIs that will be backed up or used as backups. All parameterscan be configured for each DLCI except specifying a Backup Group Number on aprimary DLCI (that will be backed up) on an "initiating" node (which will initiatethe switchover to a backup DLCI).2. Configure backup groups. A backup group is one or more DLCIs that will act asbackup if the primary goes down.3. Configure Backup Group Numbers and related information for primary DLCIs.This will assign a Backup Group to each primary DLCI.For each example in Figure 7-1, assume that Node 1 is a remote site and Node 2 is acentral site. Also assume that Node 1 will be the initiating node. On that node, theprimary DLCI is on port 2 and the backup is on port 0.31 20 20 16 16 25
