Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Руководство по настройке

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page 59. For information about the default value for each command, see the
command descriptions in “Configuring VC Classes” on page 59.
Precedence Levels for Dynamic PVCs
For PVCs that are dynamically created, the router determines the PVC attribute values
according to the following precedence levels, in order from highest precedence to
lowest precedence:
1.
The attribute value specified in the VC class assigned in the base profile always
has the highest precedence.
2.
If no VC class is assigned in the base profile, the router takes the value for that
attribute from the VC class assigned to the associated ATM major interface.
3.
If neither the base profile nor the ATM major interface has a VC class assigned,
the router takes the value for that attribute from the individually specified
attributes in the base profile.
4.
If neither the base profile nor the ATM major interface has a VC class assigned,
and no attributes are individually specified in the base profile, the router applies
the default values for the commands listed in Table 8 on page 59. For information
about the default value for each command, see the command descriptions in
“Configuring VC Classes” on page 59.
Precedence Level Examples
For examples that illustrate how precedence levels affect the assignment of VC
classes, see “Precedence Level Examples for Assigning VC Classes” on page 67.
To help you better understand these examples, we recommend that you first read
the following sections to learn how to configure and assign VC classes:
Upgrade Considerations
The following considerations apply to using ATM VC classes when you upgrade to
the current JUNOSe software release from a lower-numbered JUNOSe software
release:
■
It is possible to use VC classes for PVCs created in a lower-numbered release
with the
atm pvc command. In such cases, the router uses the following rules
to determine the PVC attribute values:
■
Nondefault values explicitly specified for PVC attributes with the atm pvc
command take precedence over the attribute values specified in the
associated VC class. As a result, the router takes the values for these attributes
from the
atm pvc command settings.
■
Default values implicitly specified for PVC attributes with the atm pvc
command have a lower precedence than the attribute values specified in
the associated VC class. As a result, the router takes the values for these
attributes from the assigned VC class.
■
The output of the show configuration command uses either the pvc command
format or the atm pvc command format to display ATM PVCs. The display format
Configuring ATM VC Classes
■ 57
Chapter 1: Configuring ATM