The SMI on Switches

Each switch implements a special management port, port 0. This is the only switch port that implements a Transport Layer as it is the only switch port that implements QPs. Those QPs are QP0 (the SMI) and QP1 (the GSI). Switch port 0 has some other special qualities:

• It is typically implemented as a strictly internal port with no Physical Layer.

• It is the only switch port that is assigned a LID address by the SM. It should be noted that although a base LID address is assigned to switch port 0 by the SM, this port does not implement the PortInfo.LMC field, so it cannot be assigned a range of LID addresses.

The other switch ports are not addressable and merely act as conduits for receiving and forwarding packets. When a switch port other than port 0 receives an inbound SMP or GMP, the packet's LRH:DLID address is used to direct the packet. See “Switch Handling of an Inbound Request SMP” on this page.