Scenarios

The following scenario and questions are designed to draw together the content of the chapter and exercise your understanding of the concepts. There is not necessarily one right answer. The thought process and practice in manipulating the concepts is the goal of this section. The answers to the scenario questions are found at the end of this chapter.

Scenario 20-1

Q1:

Figure 20-9 illustrates your network diagram. Your ISP gives you an address range of 2001:1BE0:3A0::/48. The edge routers also have addresses assigned on the links through which they connect to the ISP; these addresses are in a different address space. Subnet your assigned IPv6 space for this network and be sure to support summarization.

Figure 20-9. An IPv6 Network to Address

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Scenario 20-1 Answers

Figure 20-10 shows one solution for IPv6 subnet assignment on each of the links in this network. (Of course, this problem could have been solved in many other ways.) All network prefixes use the ISP assigned address space 2001:1BE0:3A0::/48, with the subnet assignment (shown as hexadecimal numbers in boxes on the diagram) as the next 16 bits, resulting in a /64 prefix.

Figure 20-10. One Solution to the IPv6 Network in Figure 20-9

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To illustrate the address assignments, the addresses of the interfaces on the top core router are as follows (the subnet field is highlighted):

Fa0/0: 2001:1BE0:03A0:0000::1/64
Fa0/1: 2001:1BE0:03A0:0001::1/64
S1/0: 2001:1BE0:03A0:0010::1/64
S1/1: 2001:1BE0:03A0:0011::1/64
S1/2: 2001:1BE0:03A0:0012::1/64
S1/3: 2001:1BE0:03A0:0013::1/64
Anycast address on all serial interfaces: 2001:1BE0:03A0:0030::1/64

The addresses on the top internal router are as follows:

Fa0/0: 2001:1BE0:03A0:0040::1/64
S1/0: 2001:1BE0:03A0:0010::2/64
S1/1: 2001:1BE0:03A0:0020::2/64

Note the following points:

All network prefixes are derived from the ISP assigned address space 2001:1BE0:3A0::/48.
The two core routers have the same anycast address configured on their serial links (on subnet 0x0030), for routing redundancy.
The two edge routers have the same anycast address configured on all of their interfaces connected to the internal network (on subnet 0x0004); this can be used for routing redundancy.
Summarization is supported. For example, each of the two core routers could summarize the subnets via which they connect to the internal network. The top core router's summary route for its internal networks is 2001:1BE0:3A0:0010::/60, and the lower router's summary route for its internal networks is 2001:1BE0:3A0:0020::/60.