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mask vs. wildmask

Here OSPF Commands-

#network network-number wildcard-mask area area-id

and

#area area-id range address mask

Which reason to use in one case mask and in the other - wildcard-mask? Why not use everywhere mask or wildcard-mask? :-)

2 REPLIES

Re: mask vs. wildmask

Hi,

my understanding is Cisco believes wildcards are more flexible. You can match comparing three bits in the middle of IP address, e.g., which might help you to select "interesting" addresses. That's why wildcards have been "invented" and are used to choose the interfaces which run OSPF by the "network" command.

Address summarization via range command is supposed using well-known and simple address masks, I think.

Regards,

Milan

New Member

Re: mask vs. wildmask

The reason has to do with the application each of the commands has.

The command lets you aggregate addresses. All aggregates are a contiguous set of sub-blocks, so we use a mask (contiguous set of bits).

The command lets you enable OSPF on specific interfaces. In some cases not all the interfaces belonging to an area may be part of the same (contiguous) block, so the flexibility of a wildcard-mask comes in.

For example, "network 200.200.200.0 0.0.64.255 area 5" is a valid command, but "area 5 range 200.200.200.0 255.255.191.0" is not.

Alvaro.

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