3Com CoreBuilder 9000 User Manual page 394

394 C 15: LAN E
HAPTER MULATION
LES Redundancy When a network has more than one CoreBuilder 9000 ATM Enterprise
Facility — Switch, you can create redundant LESs for an ELAN. When you designate
Configuring the ELAN a primary LES in a switch to be the active LES for an ELAN, you can
Topology Database designate a secondary LES in another switch to be the backup or
redundant LES for the ELAN. In case the switch with the active LES of an
ELAN fails, the secondary LES is activated; the ELAN continues to operate
and the interrupted calls are reestablished.
You plan out LES redundancy for an ELAN by identifying a primary and
secondary LES, each of which can serve as an active LESs for that ELAN.
The primary LES has the highest priority to be the active LES for that
ELAN.
When you set up the network, you enter the primary and secondary LES
in the topology database of the LECS of each switch in which it is
enabled, using either the LMA or, preferably, the Transcend Enterprise
Manager application. This way, each LECS has the same information
about the LESs associated with each ELAN and can take over as the active
LECS at any time.
LMA Commands
To enter the primary LES by LMA, see "Add ELAN" on page 256; to enter
a secondary LES, see "Assign Redundant LES to ELAN" on page 264.
Shared LES
You may assign a LES to two different ELANs: as a primary LES for the first
ELAN and as the secondary LES for the second ELAN or as a secondary
LES for more than one ELAN. Such a LES is called shared between the two
ELANs.
CAUTION: 3Com recommends that you do not use shared LESs unless
there are insufficient ELAN resources in the network. Shared LESs can, in
certain circumstances, cause two ELANs to collapse into one or make it
difficult to recover from a split ELAN.