Cabletron Systems SmartSwitch 9A100, User Manual

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SmartSwitch 9A100 User Guide 4-15
Switch Administration PVC Connections
4.5.4 Non-zero VPIs
The SmartSwitch 9A100 uses 12 bits to define VPI/VCI pairs. The
vccmask
determines how many of the 12 bits are
used for the VPI and how many are used for the VCI. The
vccmask
uses a 2-bit register to hold four different VPI/VCI
12-bit combinations. Table 4-1 shows the registers and the values that come preconfigured on the SmartSwitch 9A100.
Use the
show vccmask
command to view the four preconfigured VPI/VCI combinations.
SmartSwitch # show vccmask
MaskIndex VpiShift VciShift
(In bits) (In bits)
============================================================================
0 0 12
1 2 10
2 4 8
3 6 6
SmartSwitch #
VCCMask combinations dictate what numerical values can be used for VPI/VCI pairs. Any VPI and VCI pairs that fit
the bit distribution of one of the indexed combinations can be used for defining a PVC. If the VPI and VCI values do
not fit one of the indexed combinations, the SmartSwitch 9A100 uses the closest matching indexed combination.
If you need to use values for VPI and VCI that do not fall within the range of one of the preconfigured indexed
combinations, use the
set vccmask
command to replace one of the preconfigured combinations.
For example, change VCCMask indexed combination zero (0) from VPI = 0 bits and VCI = 12 bits to
VPI = 3 bits and VCI = 9 bits.
1. Use
set vccmask
to change the VPI/VCI values to 3/9.
SmartSwitch # set vccmask
MaskIndex(0) :
<we replace the first VPI/VCI pair
VPIShift(0) : 3
VCIShift(12) : 9
SmartSwitch #
2. Use the
show vccmask
command to see the new VPI/VCI combination.
SmartSwitch # show vccmask
MaskIndex VpiShift VciShift
(In bits) (In bits)
============================================================================
0 3 9
<for index 0, VPI/VCI now equals 3/9
1 2 10
2 4 8
3 6 6
SmartSwitch #
Table 4-1 Values for VPI and VCI
VCC Mask Index VPI Bits VPI Values VCI Bits VCI Values
0 0 0 12 0 to 4096
1 2 0 to 3 10 0 to 1023
2 4 0 to 15 8 0 to 255
3 6 0 to 63 6 0 to 63