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rjkumar89
Beginner

loopback ip range??

Hi all,

We all know the ip address range and structure of IPv4

In that 127.x.x.x is reserved for loop back ip address for hosts,but commonly we use 127.0.0.1 as a loop back ip address in hosts to check the interface and network card.

Can any one explain me,Why the whole block is reserved for loop back address i.e 127.0.0.0 block which contain 16777214 hosts.

Regards,

Rajkumar.

3 REPLIES 3
Leo Laohoo
VIP Community Legend

Duplicate post.

Sent from Cisco Technical Support iPad App

The IP address 127.0.0.1 is a special purpose address reserved for use  on each computer. 127.0.0.1 is conventionally a computer's loopback  address.

Network software and utilities can use 127.0.0.1 to access a local  computer's TCP/IP network resources. Messages sent to loopback IP  addresses like 127.0.0.1 do not reach outside to the local area network  (LAN) but instead are automatically re-routed by the computer's own  network adapter back to the receiving end of the TCP/IP stack.

Typically all IP addresses in the range 127.0.0.1 - 127.255.255.255 are  reserved for private use, but 127.0.0.1 is by convention the loopback  address in almost all cases.

Angello1812
Beginner

Hi Rajkumar

127.0.0.0/8 is simply defined as loopback network by RCF 3330. For more detailed infomations, you can read that document . Basically you can try to ping any IP address, not just 127.0.0.1 and it will work as loopback, they are all mapped on it.

Karthikeyan, that private range you are talking about is 172.16.0.0/12 . Loopback range in general is not reserved for private ip addresses. Actually to be honest I've never heard or read about that use. Feel free to correct me if I'm wrong.

Hope I helped

Regards

Jan Janovic