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8.9.3 Beacon Recovery in the 8260
Beacon recovery in the 8260 has been improved by distributing the beacon
recovery process to each of the 8260 token-ring media modules (both active and
passive). This allows you to manage an 8260 consisting of multiple token-ring
segments using a single DMM and protect multiple rings from beacon problems
without the need to have one DMM for each segment.
Each 8260 token-ring media module has a built-in chip called Recovery ASIC
(Application Specific Integrated Circuit) which provides beacon recovery for the
stations attached to that media module.
8.9.3.1 Recovery ASIC
The recovery ASIC has two entities. These two entities are called ″Upstream
Recovery ASIC″ or URA and ″Downstream Recovery ASIC″ or DRA. Both
entities have a burnt-in MAC address. These MAC addresses are only used for
beacon recovery and do not limit the maximum number of MAC addresses on a
ring.
In the case of module switching modules, the Recovery ASIC is always attached
to the ring configured for that module and the URA is located between the
backplane and the first port of the module while DRA is located between the
backplane and the last port of that module. This is shown in Figure 93.
Figure 93. Recovery ASIC in Module Switching Module
In the case of per-port switching modules, as the ports on the module can be
attached to multiple backplane segments, the Recovery ASIC is not connected to
any of the backplane rings under normal operating conditions. Instead,
associated with each port is a function called Ring Monitor (see 8.9.3.2, “Ring
Monitor on the Per-Port Switching Module” on page 157 for details) which is
placed upstream of its associated port and monitors for beaconing condition. As
soon as a beacon condition is detected on one of the rings to which this
module′s ports are attached, then the Recovery ASIC will be inserted into that
ring to provide the beacon recovery function. In this case, the DRA will be
placed between the backplane and the last port of this module on the beaconing
ring. Also, the URA will be inserted into the backup path if ports 17 and 18 are
configured as trunk ports. This is shown in Figure 94 on page 156.
Chapter 8. 8260 Token-Ring Support 155