Designing Cisco Network Service Architectures - Free Books

Each Region of 500 hotels is assigned address blocks as follows:Region Address Block Total Addresses in Block Active Desktop and Access Ports1 10.96-103 2,097,152 Up to 128,000 (500 x 256)2 10.104-111 2,097,152 Up to 128,0003 10.112-119 2,097,152 Up to 128,0004 10.120-127 2,097,152 Up to 128,000This matches to a bit mapping design of 10.011r raaa.aass ssss.hhhh hhhh, where “r” indicatesthe region bits (region minus 1), “a” indicates the area bits within that region, “s” indicates thesubnet bits relative to the area, and “h” indicates the host bits in the subnet.Within each region, the 5 area bits allow for 32 areas (16 plus area 0 forces us up to 32,however, or 6 bits). Within each area, we need to connect 32 or fewer hotels, which means weneed 32 subnets (5 subnet bits, make it 6 to allow more flexibility, and also provide /30 blocksfor the WAN links).18 Designing Cisco Network Service Architectures (ARCH) v2.0 © 2007 Cisco Systems, Inc.