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ccna certification in india.This is because other routing protocols use link-local addresses to establish neighbor relationships and exchange routing information, and link-local addresses do not meet the addressing requirements of 6to4 addresses, so 6to4 tunnels cannot be established.(4) ISATAP TunnelsISATAP (Intra-Site Automatic Tunnel Addressing Protocol) is another IPv6 automatic tunneling technology, which is also used to connect isolated IPv6 networks through IPv4 networks. Similar to 6to4 addresses, ISATAP addresses have IPv4 addresses embedded in them, which makes it easy for border devices to obtain the destination address for establishing a tunnel and thus automatically create a tunnel. But the address formats for these two automatic tunnels are different. 6to4 uses an IPv4 address as the network ID, while ISATAP uses an IPv4 address as the interface ID° The interface ID of an ISATAP address consists of 0000:5EFE and the IPv4 address (in hexadecimal), where 0000:5EFE is a dedicated OUI that identifies the ISATAP address for IPv6, for example, the border device's IPv4 address is 192.168.99.1, then the 64-bit interface ID is 0000:5EFE:c0a8:6301.3. IPv4/IPv6 Protocol Translation TechnologyNAT-PT (Network Address Translation-Protocol Translation) is a transition method for direct communication between IPv4 and IPv6 networks, that is, the original IPv4 network does not need to be upgraded, and all the conversion work including address and protocol is done by NAT-PT network devices. The NAT-PT device issues a "/96" routing prefix to the IPv6 network, and all IPv6 packets with this prefix are sent to the NAT-PT device. The NAT-PT device, in order to support the NAT-PT function, also has a pool of IPv4 addresses that are used when forwarding packets from the IPv6 network to the IPv4 network. In addition, DNS-ALG (DNS-Application Layer Gateway) is typically implemented in the NAT-PT device to help provide name-to-address mapping that plays a role in the IPv6 network's access to the IPv4 network. NAT-PT is divided into static NAT-PT and dynamic NAT-PToChapter 3 Device Access and IOS ConfigurationTo configure a network device, you must first be able to connect to the appropriate device before you can access the configuration interface to begin the configuration process. In practice, it is common to first connect through the console (Console) port of the network device to perform some initial configuration, and subsequent tasks can be performed by remotely logging in (Telnet or SSH) to the network device for configuration and management, however, some tasks, for example, network device password recovery or IOS recovery after deletion, can only be handled by connecting to the Console port to handle. The Cisco network device comes with the powerful CiscoIOS operating system software, which provides a large number of commands that you should be familiar with to be able to function well with the network device. This chapter first introduces the way to access Cisco network devices, and then introduces the functions of IOS, naming, basic commands and their management methods.3.1 Access to Cisco network devices wayA router or switch is a special-purpose computer, however, they do not have a keyboard, mouse, and monitor, and require the appropriate components of the computer to complete the configuration. Network devices are usually shipped without initial configuration (Cisco's latest routers already have some initial configuration for remote login), and to complete the initial configuration you need to connect the computer's serial port (COM port) to the router's console (Console) port, or if the computer does not have a COM port, you need to prepare a USB to COM cable and its corresponding driver. After the initial configuration of the IP address and password of the interface is completed, you can use other methods such as TelnetsSSH, Web browser, and network management software (e.g. CiscoWorks) to configure the network device.3.1.1 Accessing Network Devices through the Console Port The Console port is a type of management port for network devices that allows out-of-band (OutofBand, 00B) access to Cisco devices. The COM port of a computer and the Console port of a router or switch are connected via a reversed (the wire sequence on the RJ45 connectors at each end of the cable is reversed) cable, with one end of the reversed cable connected to the Console port of the router and the other end connected to the COM port of the computer, as shown in Figure 3-1. Most of the laptops nowadays do not have serial ports anymore, so you need to use a USB to serial adapter. If connecting to the device through the Mini-B USB Console port (see Figure 1.3), you need to prepare