This read-only value reports the maximum VPI the signalling stack may currently allocate to switched virtual path connections, computed as the minimum of this interface's own configured maximum and its UNI/NNI peer's configured maximum, or a fixed value if the interface doesn't negotiate. Because it's the minimum of both sides, this is the actual usable ceiling for new switched virtual paths right now, and it can be lower than what was configured locally if the peer is more restrictive, exactly the object to check when SVPC setups are being rejected for exceeding VPI range despite a seemingly generous local configuration. A local configuration of 20 combined with a peer only willing to negotiate up to 8 would leave this object reading 8, and any SVPC setup attempt requesting VPI 15 would fail.