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I am learning about OSPF Routing which is a dynamic routing protocol.

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I have questions with regards to commands on the router:

Why do the commands end with 0.0.0.255 area 0?

What does 0.0.0.255 mean?

What does area 0 mean?

Ron Maupin
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Computernerd
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    short answer: many people are lazy – Mike Pennington May 30 '15 at 00:51
  • Did any of the answers help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively you can answer your own question and accept the answer. – Ron Maupin Aug 06 '17 at 02:45

1 Answers1

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An OSPF domain is broken up into areas, and every area connects to area 0. The area portion of the command tells OSPF which area to put the interface(s) using address(es) in that range into.

The "0.0.0.255" is a wildcard mask (inverse of the prefix mask). It tells OSPF the range to use for selecting the interfaces for that network statement. The "network 10.0.1.0 0.0.0.255 area 0" means any interfaces in the 10.0.1.0/24 prefix will be in area 0.

Ron Maupin
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  • Wildcard mask is not just the inverse of network mask. For instance: 0.0.255.0 is a valid wildcard mask while 255.255.0.255 is not a valid network mask. You can check http://networkengineering.stackexchange.com/q/771/76 – Daniel Yuste Aroca May 30 '15 at 07:04
  • That is true, but I didn't feel the need to confuse the OP since the use of non-contiguous masks is rare in the real world. The tricks that can be played with non-contiguous masks are almost never worth the maintenance problems they can create. You may have noticed that IPv6 has dropped the use of masks as unnecessary. – Ron Maupin May 30 '15 at 20:29