3Com CoreBuilder 9000 User Manual page 395

Atm enterprise switch
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Assigning the Active LES for an ELAN — Monitoring LES Status
On-line
Before it assigns the primary or secondary LES of an ELAN to be active,
the LECS determines if they are operational. For this purpose, each LECS
continuously monitors the operating status of all LESs in its topology
database by trying to establish a ATM point-to-point connection with the
LES. If the connection is successful, the LES is marked operational. If the
attempted connection is not successful, or if an established connection is
released by the LES, the LES is identified as not operational. If the
attempted connection to a LES is not successful at first, the LECS keeps
trying to establish the connection.
If the primary LES for an ELAN is marked operational, the LECS assigns it
as the active LES and the secondary as the redundant LES, otherwise the
secondary LES is assigned as active. If both primary and secondary LESes
are not operational, an error message is returned to any LEC that requests
to join the ELAN.
Assuming that the required network connectivity exists, all LECS make
the same choices for active and redundant LESs for each ELAN in their
(identical) topology databases so that every LECS has the same picture of
the network topology.
Verifying the Active Status of a LES
To resolve a split ELAN, as described on page 398, the LECS needs to
know if a LES actually has LECs attached to it. This information is
transmitted by the LES to the LECS over the same ATM connection that
the LECS established to it. A LES with LECs connected to it periodically
transmits an ACTIVE_LES message, which contains the number of its
LECs, to all LECS that are connected to it. If an active LES has no LECs
associated with it, it does not send an ACTIVE_LES message.
Table 58 shows the LES information for an ELAN in the LECS topology
base.
:
Table 58 LES Information in LECS Topology Base
LES ID
Priority
LES 1
Primary
LES 2
Secondary
LAN Emulation Redundancy
Is LES
Assigned to be
Operational?
active LES
Yes
Yes
Yes
No
395
Number of
LECs attached
20
0

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