Global Routing: Source/Destination CAs in Different Subnets
Refer to Figure 8-2 on page 144. In this example scenario, the packet is originated by a CA in one subnet and is targeting a CA in another subnet. The packet must transit two routers to get to its destination.
Figure 8-2. Inter-Subnet Packet Example
LID Only Permits Addressing Port in Same Subnet
Using a LID to address the destination port only permits another port within the same subnet to be addressed. In the example, however, the destination port resides in another subnet. It should be obvious that additional address information is required when a packet targets a port in another subnet. ...