An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 172.16.91.0 255.255.255.192. What wildcard mask would the administrator use in the OSPF network statement?

 

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 172.16.91.0 255.255.255.192. What wildcard mask would the administrator use in the OSPF network statement?

  • 0.0.0.15
  • 0.0.0.7
  • 0.0.0.3
  • 0.0.0.63
Explanation & Hint:

A wildcard mask is used in OSPF configurations to indicate which IP addresses should be included in OSPF advertisements. It is the inverse of the subnet mask.

For the subnet mask 255.255.255.192, the binary representation is 11111111.11111111.11111111.11000000. When we invert this, we get the wildcard mask:

00000000.00000000.00000000.00111111

This translates to the wildcard mask 0.0.0.63 in decimal. Therefore, the administrator would use a wildcard mask of 0.0.0.63 in the OSPF network statement to advertise the network 172.16.91.0 with a subnet mask of 255.255.255.192.

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