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Community Member

Unable to add Loopback interface

Hi all,

i am trying to add loopback interface 0  and asisgn it IP address here is issue

2620Router(config-if)#  ip address 172.16.0.0 255.55.0.0

Bad mask 0xFF370000 for address 172.16.0.0

How can i fix this?

Thanks

Mahesh

2 ACCEPTED SOLUTIONS

Accepted Solutions
VIP Super Bronze

Unable to add Loopback interface

Hi Mahesh,

172.16.0.0/16 is a network/subnet You need to assign a host address to the interface

try this:

interface Loopback0

ip address 172.16.1.1 255.255.255.255

HTH

Purple

Unable to add Loopback interface

Hi,

your IP didn't work because:

1) it was not a host IP address but a network or subnet IP

AND

2) your mask was incorrect: 255.55.0.0 it should have been 255.255.0.0 because in a mask you must have contiguous bits

which is not the case in 55( 00110111) and the message was giving you your wrong mask in hex representation

0xFF370000 is 255.55.0.0 in dotted decimal.

Provided point 1 was corrected you could have put any valid mask  for a subnet in which the IP was included like a /24 for example. But it's best practice and in some cases mandatory like in MPLS VPNs to give loopbacks a /32 mask.

Regards.

Alain

Don't forget to rate helpful posts.
4 REPLIES
VIP Super Bronze

Unable to add Loopback interface

Hi Mahesh,

172.16.0.0/16 is a network/subnet You need to assign a host address to the interface

try this:

interface Loopback0

ip address 172.16.1.1 255.255.255.255

HTH

Community Member

Unable to add Loopback interface

Hi Reza,

that worked can you please  explain me why my IP  does not work and urs worked?

thanks

mahesh

Purple

Unable to add Loopback interface

Hi,

your IP didn't work because:

1) it was not a host IP address but a network or subnet IP

AND

2) your mask was incorrect: 255.55.0.0 it should have been 255.255.0.0 because in a mask you must have contiguous bits

which is not the case in 55( 00110111) and the message was giving you your wrong mask in hex representation

0xFF370000 is 255.55.0.0 in dotted decimal.

Provided point 1 was corrected you could have put any valid mask  for a subnet in which the IP was included like a /24 for example. But it's best practice and in some cases mandatory like in MPLS VPNs to give loopbacks a /32 mask.

Regards.

Alain

Don't forget to rate helpful posts.
Community Member

Unable to add Loopback interface

Hi,

Many thanks again Reza and alain.

regards

mahesh

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