Case Study Discontiguous Subnets and Classless Routing

Figure 7.16 shows that two Ethernets are connected to each of the four new routers. At each site, one Ethernet is a member of subnet 172.25.150.0/24 and will have no more than 12 hosts. This is easy enough. Four unused subnets are chosen from Figure 7.13 and assigned.

Figure 7.16. Cochiti, Isleta, Jemez, and Tesuque are each attached to two Ethernets. One Ethernet at each router is a member of subnet 172.25.150.0/24, and the other is a member of network 192.168.50.0/24.

Figure 7.16. Cochiti, Isleta, Jemez, and Tesuque are each attached to two Ethernets. One Ethernet at each router is a member of subnet 172.25.150.0/24, and the other is a member of network 192.168.50.0/24.

The other Ethernet at each site is a member of network 192.168.50.0 and will have no more than 25 hosts. Subnets 192.168.50.64/26 and 192.168.50.128/26 are being used, which leaves 192.168.50.0/26 and 192.168.50.192/26. By increasing the mask to 27 bits, these two subnets can be divided into four, each with five host bits—enough for 30 host addresses per subnet. Figure 7.17 shows the four subnets in binary.

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