Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Configuration Manual

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At least one currently active subscriber logs out, which causes the router to tear
down the dynamic interface column for that subscriber. Although the dynamic
ATM 1483 subinterface and its associated VC remain configured on the router,
the subinterface becomes inactive and can be replaced by one of the
bulk-configured VCs waiting to become active.
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The router tears down at least one dynamic interface column in its entirety,
which involves administratively shutting down the associated dynamic ATM 1483
subinterface.
When either of these conditions occurs, the router enables the first inactive
bulk-configured VC that receives traffic to connect to the router as a replacement for
the subscriber that logged out.
Example
Consider an ATM line module that supports a maximum of 32,000 individual VCs
created from bulk-configured VC ranges, of which only 8000 VCs can be active at
any one time. If all 32,000 bulk-configured VCs attempt to connect to the router,
only the first 8000 VCs to receive traffic are able to log in, generate dynamic
subinterface columns, and become active. When a subscriber connected through
one of these active VCs logs out, the router enables the first of the remaining 24,000
inactive bulk-configured VCs that receives traffic to connect. The router replaces the
inactive dynamic ATM 1483 subinterface and associated VC that remain after the
subscriber logout with a new dynamic ATM 1483 subinterface and its newly activated
circuit.
Combination of Static ATM 1483 Subinterfaces and Bulk-Configured VC
Ranges
ATM line modules are sometimes configured with a combination of static ATM 1483
subinterfaces and bulk-configured VC ranges. In these configurations, both the static
ATM 1483 subinterfaces and bulk-configured VC ranges can support active
subinterfaces. The combined total of active static ATM 1483 subinterfaces, and active
dynamic ATM 1483 subinterfaces created from bulk-configured VC ranges, cannot
exceed the maximum number of active subinterfaces supported by the line module.
The number of active dynamic subinterfaces created from the bulk-configured VC
ranges is limited by both of the following:
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The number of static ATM subinterfaces that exist on the line module, which
cannot exceed the maximum number of configured ATM 1483 subinterfaces
supported on the line module.
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The number of static ATM subinterfaces that are active on the line module, which
cannot exceed the maximum number of active ATM 1483 subinterfaces supported
on the line module.
Example
Consider an ATM line module that supports a maximum of 8000 active ATM 1483
subinterfaces. The module has 4000 static ATM 1483 subinterfaces configured, all
of which are active, and 8000 individual VCs created from bulk-configured VC ranges.
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Overview
JUNOSe 11.1.x Link Layer Configuration Guide