Learning by Doing: CISCO Certified Network ... - SCN Research

2. We can use a loopback interface as a “logical” interface. We can use whatever
address we want with loopback addresses (ie., 1.1.1.1, 240.21.2.2, etc). So let’s
configure a loopback interface:
Bell(config)#int loop 0
Bell(config-if)#ip address 1.1.1.1 255.255.255.0
Bell(config-if)#no shut
We really do not have to add the “no shut” since these are logical interfaces, but
its good practice to always “no shut” anytime you are configuring an interface.
Exit from the configuration mode and ping from the router to the looback
interface. You should see:
Bell#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
Bell#
Ping from the workstation to the loopback interface. You should see:
C:\WINDOWS\Desktop>ping 1.1.1.1
Pinging 1.1.1.1 with 32 bytes of data:
Reply from 1.1.1.1: bytes=32 time=2ms TTL=255
Reply from 1.1.1.1: bytes=32 time=1ms TTL=255
Reply from 1.1.1.1: bytes=32 time=1ms TTL=255
Reply from 1.1.1.1: bytes=32 time=1ms TTL=255
Ping statistics for 1.1.1.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 2ms, Average = 1ms
C:\WINDOWS\Desktop>
3. We can do more…add these in and try to ping (from DOS) to each looback
interface from your workstation:
Loopback 1 11.11.11.11/24
Loopback 2 22.22.22.22/24
Loopback 3 33.33.33.33/24
Loopback 4 44.44.44.44/24
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