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loopback interface issue?

     why we can create only one loopback interface in one network/subnetwork?

2 REPLIES
Cisco Employee

Re: loopback interface issue?

The difference between Loopback and any other interface on a router is that loopback is a 'logical' interface. With routers you cannot have two interfaces with overlapping address space so the same logic applies when you configure multiple loopback interfaces, these need to be addressed out of unique address space. You can play with the subnet mask to conserve address space while addressing loopbacks but you cannot have overlapping subnets.

Hall of Fame Super Blue

Re: loopback interface issue?

prashantdwivedi wrote:

     why we can create only one loopback interface in one network/subnetwork?

It just depends on what subnet  mask you use ie. you cannot do this on the same device -

int loopback 10

ip address 192.168.5.1 255.255.255.0

int loopback 11

ip address 192.168.5.2 255.255.255.0

but you can do this -

int loopback 10

ip address 192.168.5.1 255.255.255.255

int loopback 11

ip address 192.168.5.2 255.255.255.255

Jon

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