About this interactive
A wildcard mask marks which bits of an address must match (0) and which are wild (1). For a network it is usually the subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255, and 255.255.255.248 becomes 0.0.0.7. Subtract each octet from 255.
- **One host**: 0.0.0.0, every bit must match.
- **One subnet**: the inverse of its mask.
- **A summary**: more wild bits than any one subnet, such as 0.255.255.255 for all of 10.0.0.0/8.
- **Any address**: 255.255.255.255.
OSPF network statements use wildcard masks now, and access control lists use them in a later module.
What you'll learn
- Convert a subnet mask or prefix length to a wildcard mask, and a wildcard mask back to its subnet mask
- Read what a wildcard mask matches: one host, one subnet, a summary range or every address, and whether a given address falls inside
Aligned to
Cisco CCNA
3.4
Configure and verify single area OSPFv2
5.6
Configure and verify access control lists
Key terms
- Wildcard Mask
- A 32-bit mask used in ACL statements and OSPF network commands where a 0 bit means the corresponding address bit must match and a 1 bit means it can be anything. Wildcard masks are the inverse of subnet masks and allow a single statement to match an entire range of IP addresses.
- OSPF Network Statement
- A configuration command that identifies which interfaces and directly connected networks will participate in the OSPF routing process.
- Host Route
- A route that specifies a single specific host, identified by a /32 prefix in IPv4 or /128 in IPv6, rather than an entire network.
Topics
Ospf
Wildcard Mask
Subnetting
Acl
Interactive
Calculation
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