Cabletron Systems 9032578-05 manual Creating a Non-Zero VPI, Setting the Bit Allocation for VPI

Creating a Non-Zero VPI

Creating a Non-Zero VPI

The Virtual Path Identifier defines a virtual path, a grouping of virtual channels transmitting across the same physical connection. The actual number of virtual paths and virtual channels available on an ATM port depends upon how many bits are allocated for the VPI and VCI, respectively. By default, there are 0 bits allocated for VPI and 12 bits allocated for VCI. You can specify a different allocation of bits for VPI and VCI for a port.

There are 12 bits available for each VPI/VCI pair per port. The number of bits allocated define the amount of VPI and VCI values available. The following equations define the number of virtual paths and virtual channels:

#of virtual paths = 2n; where n is the number of bits allocated for VPI

#of virtual channels = 2(12-n); where (12-n) is the number of bits allocated for VCI

The bit allocation command allows you to set the number of bits allocated for VPI; the remaining number of bits are allocated for VCI. Since there are only 12 bits available for each VPI/VCI pair on an ATM port, the more bits you allocate for VPI, the fewer bits remain for VCI.

Setting the Bit Allocation for VPI

To set the bit allocation for VPI on an ATM port, enter the following command in Configure mode:

Sets the number of bits allocated for VPI on a port.

atm set port <port list> vpi-bits <num>

The following is a description of the parameter used to set the number of bits allocated for VPI on an ATM port:

port <port list> This parameter identifies the ATM port. Specify this parameter in the format: media.slot.port. Specify all-portsto set bit allocation on all ports.

media Specifies the media type. This is at for ATM ports.

slot Specifies the slot number where the module is installed.

port Specifies the port number.

vpi-bits<num> This parameter sets the number of bits for VPI. Specify any number between 1 and 11. The default is 1.

SmartSwitch Router User Reference Manual 47