Ccna 00-301, Volume Official

Figure 15-6

  IPv4 Addresses Used in Example 15-2

Example 15-2

  Configuring IP Addresses on Cisco Routers

R1# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

R1config)# interface G0/0

R1(config-if)# ip address 172.16.1.1 255.255.255.0

R1(config-if)# no shutdown

R1(config-if)# interface S0/0/0

R1(config-if)# ip address 172.16.4.1 255.255.255.0

R1(config-if)# no shutdown

R1(config-if)# interface G0/1/0

R1(config-if)# ip address 172.16.5.1 255.255.255.0

R1(config-if)# no shutdown

R1(config-if)# ^Z

R1#

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Chapter 15: Operating Cisco Routers    361

Example 15-3 shows the output of the show protocols command. This command confirms 

the state of each of the three R1 interfaces in Figure 15-6 and the IP address and mask con-

figured on those same interfaces.

Example 15-3

  Verifying IP Addresses on Cisco Routers

R1# show protocols

Global values:

   Internet Protocol routing is enabled

Embedded-Service-Engine0/0 is administratively down, line protocol is down

GigabitEthernet0/0 is up, line protocol is up

   Internet address is 172.16.1.1/24

GigabitEthernet0/1 is administratively down, line protocol is down

Serial0/0/0 is up, line protocol is up

   Internet address is 172.16.4.1/24

Serial0/0/1 is administratively down, line protocol is down

GigabitEthernet0/1/0 is up, line protocol is up

   Internet address is 172.16.1.1/24

One of the first actions to take when verifying whether a router is working is to find the 

interfaces, check the interface status, and check to see whether the correct IP addresses and 

masks are used. Examples 15-1 and 15-3 showed samples of the key show commands, while 

Table 15-4 summarizes those commands and the types of information they display.

Table 15-4  Key Commands to List Router Interface Status