Network Support - Cisco Catalyst 5000 Series Manual

LANE Token Ring Components
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One combined LES and BUS is required for each ELAN.
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One LECS is required for each ATM LANE switch cloud.
The LECS database can have the following types of entries:
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Note
An ELAN name must be unique on an interface. If two interfaces participate in LANE, the second interface
may be in a different switch cloud.
The server assigns individual LECs to particular ELANs by directing them to the LES for the ELAN. The
LECS maintains a database of LEC and server ATM or MAC addresses and their ELANs. A LECS can
serve multiple ELANs.
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Cisco has developed a fault tolerant mechanism known as Simple Server Redundancy Protocol (SSRP) that
eliminates these single points of failure. Although there is only one LES per ELAN, SSRP allows you to
configure redundant servers. You can configure servers to act as backup servers that become active if a
master server fails. The priority levels for the servers determine which servers have precedence.
FSSRP is an enhancement to the SSRP. With FSSRP, LECs no longer need to go down whenever there is a
change in the master LES. This uninterrupted service is achieved by connecting the LECs simultaneously
to more than one LES/BUS (up to four) so that if the master LES goes down, the backup LESs are
immediately available. With the basic SSRP, the LEC must go down and completely recycle before coming
back up. This operation is accomplished by keeping the control connections open to all of the active LESs
and BUSs in the ELAN. Although this method uses more virtual circuits (VCs), the main benefits are the
transparency and speed in the switchover.
Note
ELAN components coexist on one or more Cisco routers or Catalyst switches that contain an ATM module.
On Cisco routers or Catalyst switches the LES and the BUS are combined into a single entity.

Network Support

The Token Ring LANE on the Catalyst 5000 series ATM module feature supports the following
networking features:
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LANE broadcast and unknown server (BUS)--The BUS floods unknown destination traffic and
forwards multicast and broadcast traffic to LECs within an ELAN.
LANE Configuration Server (LECS)--The LECS contains the database that determines which ELAN a
device belongs to (each LECS can have a different database). Each LEC contacts the LECS once to
determine which ELAN it should join. The LECS returns the ATM address of the LES for that ELAN.
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ELAN name, ATM address of LES pairs
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ELAN name and the ring number of the ELAN (local-seg-id)
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LEC MAC address, ELAN name pairs
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LEC ATM template, ELAN name pairs
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Default ELAN name
Fast Simple Server Redundancy Protocol (FSSRP)--Token Ring LANE relies on three servers: LECS,
LES, and BUS. If any one of these servers fails, the ELAN cannot fully function.
LAN switching between ELANs and between a Token Ring ELAN and a legacy LAN
Network Support
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