Cabletron Systems 9A100 Non-zero VPIs, VCC Mask Index, VPI Bits, VPI Values, VCI Bits, VCI Values

Switch Administration PVCConnections

4.5.4Non-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.

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

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 #

SmartSwitch 9A100 User Guide 4-15