Switch Performs Packet Forwarding

Switch Port 0

Port 0 May or May Not Have a Physical Layer

Refer to Figure 25-22 on page 663. A switch must implement Port 0 as an internal port (optionally, it may also be implemented as an external port and could be connected to a link). It is the only switch port that is assigned a LID address (just a base address; it has no PortInfo.LMC for assigning a range of LID addresses to the port). This means it is the only switch port that can be directly addressed. The illustration shows port 0 with an optional Physical Layer and a required Transport Layer. None of the other switch ports implement a Transport Layer (i.e., they have no QPs).

Figure 25-22. Switch Port Zero Is Its Management Port
Switch Port 0's SMI ...

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