The basic addressing and configuration of Cisco devices was covered in either the Introduction to Networks or Network Basics course. However, we will spend some time reviewing these topics as well as preparing you for the hands-on lab experience in this course. Show Configure Basic Router Settings (1.1.3.1)Cisco routers and Cisco switches have many similarities. They support a similar modal operating system, similar command structures, and many of the same commands. In addition, both devices have similar initial configuration steps. When initially configuring a Cisco switch or router, the following steps should be executed: 
For example, the following commands would configure the basic settings for router R1 shown in Figure 1-14. Figure 1-14 Configuring the Basic Settings of R1 Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# hostname R1 R1(config)# R1(config)# enable secret class R1(config)# R1(config)# line console 0 R1(config-line)# password cisco R1(config-line)# login R1(config-line)# exit R1(config)# R1(config)# line vty 0 4 R1(config-line)# password cisco R1(config-line)# login R1(config-line)# exit R1(config)# R1(config)# service password-encryption R1(config)# R1(config)# banner motd $ Authorized Access Only! $ R1(config)# end R1# R1# copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] R1# Go to the online course to use the Syntax Checker in the fifth graphic to configure basic settings on R2. Configure an IPv4 Router Interface (1.1.3.2)One distinguishing feature between switches and routers is the type of interfaces supported by each. For example, Layer 2 switches support LANs and, therefore, have multiple FastEthernet or Gigabit Ethernet ports. Routers support LANs and WANs and can interconnect different types of networks; therefore, they support many types of interfaces. For example, G2 ISRs have one or two integrated Gigabit Ethernet interfaces and High-Speed WAN Interface Card (HWIC) slots to accommodate other types of network interfaces, including serial, DSL, and cable interfaces. To be available, an interface must be:
Optionally, the interface could also be configured with a short description. It is good practice to configure a description on each interface. The description text is limited to 240 characters. On production networks, a description can be helpful in troubleshooting by providing information about the type of network to which the interface is connected. If the interface connects to an ISP or service carrier, it is helpful to enter the third-party connection and contact information. Depending on the type of interface, additional parameters may be required. For example, in the lab environment, the serial interface connecting to the serial cable end labeled DCE must be configured with the clock rate command. NOTE Accidentally using the clock rate command on a DTE interface generates a “%Error: This command applies only to DCE interface” message. The steps to configure an IPv4 interface on a router are:
For example, the following commands would configure the three directly connected interfaces of router R1 shown in Figure 1-14 (in the previous section): R1(config)# interface gigabitethernet 0/0 R1(config-if)# description Link to LAN 1 R1(config-if)# ip address 192.168.10.1 255.255.255.0 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# R1(config)# interface gigabitethernet 0/1 R1(config-if)# description Link to LAN 2 R1(config-if)# ip address 192.168.11.1 255.255.255.0 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# R1(config)# interface serial 0/0/0 R1(config-if)# description Link to R2 R1(config-if)# ip address 209.165.200.225 255.255.255.252 R1(config-if)# clock rate 128000 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# Go to the online course to use the Syntax Checker in the fourth graphic to configure the R2 interfaces. Configure an IPv6 Router Interface (1.1.3.3)Configuring an IPv6 interface is similar to configuring an interface for IPv4. Most IPv6 configuration and verification commands in the Cisco IOS are very similar to their IPv4 counterparts. In many cases, the only difference uses ipv6 in place of ip in commands. An IPv6 interface must be:
NOTE An interface can generate its own IPv6 link-local address without having a global unicast address by using the ipv6 enable interface configuration command. Unlike IPv4, IPv6 interfaces will typically have more than one IPv6 address. At a minimum, an IPv6 device must have an IPv6 link-local address but will most likely also have an IPv6 global unicast address. IPv6 also supports the ability for an interface to have multiple IPv6 global unicast addresses from the same subnet. The following commands can be used to statically create a global unicast or link-local IPv6 address:
The steps to configure an IPv6 interface on a router are:
In the example topology shown in Figure 1-15, R1 must be configured to support the following IPv6 global network addresses:
Figure 1-15 IPv6 Topology When the router is configured using the ipv6 unicast-routing global configuration command, the router begins sending ICMPv6 Router Advertisement messages out the interface. This enables a PC connected to the interface to automatically configure an IPv6 address and to set a default gateway without needing the services of a DHCPv6 server. Alternatively, a PC connected to the IPv6 network can get its IPv6 address statically assigned, as shown in Figure 1-16. Notice that the default gateway address configured for PC1 is the IPv6 global unicast address of the R1 Gigabit Ethernet 0/0 interface. Figure 1-16 Statically Assign an IPv6 Address to PC1 For example, the following commands would configure the IPv6 global unicast addresses of the three directly connected interfaces of the R1 router shown in Figure 1-15: R1# configure terminal R1(config)# interface gigabitethernet 0/0 R1(config-if)# description Link to LAN 1 R1(config-if)# ipv6 address 2001:db8:acad:1::1/64 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# R1(config)# interface gigabitethernet 0/1 R1(config-if)# description Link to LAN 2 R1(config-if)# ipv6 address 2001:db8:acad:2::1/64 R1(config-if)# no shutdown R1(config-if)# exit R1(config)# R1(config)# interface serial 0/0/0 R1(config-if)# description Link to R2 R1(config-if)# ipv6 address 2001:db8:acad:3::1/64 R1(config-if)# clock rate 128000 R1(config-if)# no shutdown R1(config-if)# Go to the online course to use the Syntax Checker in the sixth graphic to configure the IPv6 global unicast addresses on the R2 router. Configure an IPv4 Loopback Interface (1.1.3.4)Another common configuration of Cisco IOS routers is enabling a loopback interface. The loopback interface is a logical interface internal to the router. It is not assigned to a physical port and can therefore never be connected to any other device. It is considered a software interface that is automatically placed in an “up/up” state, as long as the router is functioning. The loopback interface is useful in testing and managing a Cisco IOS device because it ensures that at least one interface will always be available. For example, it can be used for testing purposes, such as testing internal routing processes, by emulating networks behind the router. Additionally, the IPv4 address assigned to the loopback interface can be significant to processes on the router that use an interface IPv4 address for identification purposes, such as the Open Shortest Path First (OSPF) routing process. By enabling a loopback interface, the router will use the always available loopback interface address for identification, rather than an IP address assigned to a physical port that may go down. The steps to configure a loopback interface on a router are:
For example, the following commands configure a loopback interface of the R1 router shown in Figure 1-14 (shown earlier in the chapter): R1# configure terminal R1(config)# interface loopback 0 R1(config-if)# ip address 10.0.0.1 255.255.255.0 R1(config-if)# exit R1(config)# A loopback interface is always enabled and therefore does not require a no shutdown command. Multiple loopback interfaces can be enabled on a router. The IPv4 address for each loopback interface must be unique and unused by any other interface. Routers R1 and R2 each have two LANs. Your task is to configure the appropriate addressing on each device and verify connectivity between the LANs. What is the characteristic of an IPv4?Characteristics of IPv4
IPv4 could be a 32-Bit IP Address. IPv4 could be a numeric address, and its bits are separated by a dot. The number of header fields is twelve and the length of the header field is twenty. It has Unicast, broadcast, and multicast style of addresses.
What is the purpose of a loopback address on a Cisco router?A loopback interface is often used as a termination address for some routing protocols, because it never goes down. Another common use of a loopback address is to identify a router. For example, say you want to find out whether a particular router is up.
What is Cisco loopback IP?Loopback interface's IP Address determines a router's OSPF Router ID. A loopback interface is always up and allows Border Gateway Protocol (BGP) neighborship between two routers to stay up even if one of the outbound physical interface connected between the routers is down.
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