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cisco ccna boot camp.wasting public IP addresses - Given the abundance of IPv6 addresses, it does not matter if public addresses are wasted. However, by using private addresses, IPv6 address translation policies can be configured to easily control which devices can send traffic out and receive traffic back.Link-local addresses are a new concept introduced by IPv6. Traffic using these addresses can be transmitted over a much smaller range: only the current link (data link layer link). The router processes packets sent to link-local addresses, but does not forward them to other links. The most common uses of link-local addresses are for devices to obtain site-local or global unicast addresses, to discover the default gateway, and to discover network segmentsChapter 23 IPv6 615other Layer 2 neighbors in the network segment. When a device uses a link-local address, it must specify the outgoing interface, since each interface is connected to a "link".In the private address (FE80::/10), FEC::.FFF:: is the site-local address and FE8::.FEB:: is the link-local address. The loopback address is ::1,which is equivalent to the IPv4 address 127.0.0.1.The rest of the global addresses are unicast and anycast addresses, except for the multicast address space FF00::/8. However, IANA currently assigns only address 2000::/3 to the global pool, which represents approximately l/6 of all IPv6 addresses. o Of these global addresses, only 2001::/16 is assigned to the various Internet address allocation authorities. The global unicast address consists of two parts: the subnet ID (64 bits) and the interface ID (64 bits), as shown in Figure 23.2. The subnet ID contains the address registrar (the organization responsible for assigning addresses, such as IANA), the ISP prefix (the ISP to which the address belongs), the site prefix (the company to which the address belongs), and the subnet prefix (the subnet within the site). o Assigns an ISP prefix range to ISPs, allowing ISPs to easily aggregate their prefixes to advertise only one route to the Intemet backbone; this alleviates one of the major problems currently faced: the difficulty of aggregating the IPv4 address space currently allocated to ISPs as the Internet grows. Another ^advantage of this address allocation method is that the subnet prefix is 16 bits long and can contain up to 65536 subnets in a single site. IPv6 unicast addressesThe second half of the IPv6 address is the interface ID, which indicates the specific interface within the site. For addresses 2000::/3 to E000::/3, the 64-bit interface ID must have a value, so an address with all zero bits in the last 64 bits is not a valid IPv6 unicast address. For example, 2004:1234:5678:90AB:: is not a valid unicast address because its interface ID (the last 64 bits, i.e., the last 4 parts) is zero.The interface ID usually contains the MAC address of the interface, and this interface ID is often referred to as Extended Unique Identifier 64 (EUI-64) o Figure23.3 shows an interface ID using the EUI-64 format. the OUI of the LANNIC's MAC address is mapped to the first 24 bits of the interface ID and the value of the 7th bit is set as required: a 1 to indicate that the interface ID is unique within the site and a 0 to indicate that it is unique only locally on the link. The OUI mapping section is followed by a 16-bit value FFFEo The last 24 bits of the MAC address are mapped to the remainder of the interface ID.Global addresses are prefixed with 2000::/3. Multiple IPv6 addresses can be assigned to an interface, which includes link-local addresses, global unicast addresses, and anycast addresses O