This object is mandatory while configuring this ATM virtual
interface as caviIfType evuni(5) or evnni(6). The range of
VPI accepted by the agent depends on caviIfType.
The evuni accepts a range from 0 to 255, while the evnni accepts
a range from 0 to 4095.
The agent rejects a SET on this object for any interface other
than a evuni/evnni. A GET operation for interfaces other than a
evuni/evnni would always yield 0