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?

Last Updated: May 9, 2026
IT Exam Items Repository › Category: CCNA 3 v7 › 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?

  • 0.0.31.255
  • 0.0.0.63
  • 0.0.15.255
  • 0.0.7.255

Explanation: In OSPF, a wildcard mask is used to determine which bits of an IPv4 address must be matched to enable the protocol on an interface. The most efficient method to calculate this is to subtract the subnet mask from 255.255.255.255. For the network 172.16.91.0 with a subnet mask of 255.255.255.192, the calculation is:

  • 255.255.255.255 - 255.255.255.192 = 0.0.0.63.

This wildcard mask instructs the router to match the first 26 bits of the network address and ignore the last 6 bits.

Related exam: Enterprise Networking, Security, and Automation ( Version 7.00) - ENSA Final Exam

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