cisco ccna 300

cisco ccna 300.22.1.2 Private AddressesIPv6 took time to become a standard and was slow to be adopted when it was first introduced, even by ISPs on the Internet backbone. The main reason for IPv6's long-term failure to catch on was the great success of two short-term solutions to the address shortage: the use of private addresses to add addresses and the use of address translation to convert private addresses to public addresses.To address the address shortage, the Internet Engineering Task Force (IETF) developed RFC1918O devices must have a unique IP address in order to communicate. RFC1918 defines a private address space that any company can use internally. Table 22.1 lists the range of private addresses reserved by RFC1918, from which one Class A network, 16 Class B networks, and 256 Class C networks are available for casual use. The Class A network 10.0.0.0 alone provides more than 17 million addresses, which is more than enough to meet a company's needs.Exam Points Keep in mind the private addresses listed in Table 22.1 Private addresses are an IETF initiative to overcome the problem of limited public IP addressesChapter 22 Address Translation 585a scheme, but packets to be routed to the public network do not use private addresses; instead, private addresses must be converted. The conversion is usually done on a peripheral device such as a router or a security device such as a Cisco ASA.A major problem with RFC 1918 addresses is that they can only be used within a company and not for communication with devices in a public network such as the Internet. With this in mind, they are often referred to as private addresses. For example, if you send a packet with an RFC1918 address to an ISP, the ISP will either filter it out or be unable to send the returned traffic to your device. Given that many devices using private addresses need to send traffic to and receive traffic from the public network, this can obviously lead to connectivity problems.Table 22.1 RFC 1918 Private Address Classes. Address RangeClass A 10.0.0.0.10.255.255.255Class B 172.16.0.0.172.31.255.255