CCNP - Wildcard mask question

Author

Wildcard mask question

SurfinUSA

2002-04-27, 11:55 pm

Guys, when configuring these protocols, I usually see a 'network 192.168.10.0 0.0.0.255' with just 0s and 255s. But I have come across a different situation now that has a subnet mask of 255.255.255.254. Am I supposed to take the direct inverse for config of routing protocol? For example, with 255.255.255.254, do I say 'network 192.168.10.0 0.0.0.3? I came across this in a cisco related article. Any insight?

guitarjim

2002-04-28, 3:32 am

Your real close. A 31 bit subnet mask /254 only allows for a network number and a broadcast and no hosts. I don't know of any use for it.
31 bit mask:
11111111.11111111.11111111.11111110

Use a 30 bit subnet mask /252 instead:
192.168.10.0 network
192.168.10.1 1st host
192.168.10.2 2nd host
192.168.10.3 broadcast
2 host networds are good for directly connected serial interfaces.

Use the wild bit mask like you had.
192.168.10.0 0.0.0.3

The '0's mean these bits must match and the '1's mean it doesn't matter what these are.

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