Subnet Mask vs Wildcard Mask

Something I find I struggle with is when to use a subnet mask and when to use a wildcard mask. This article is to simply set out the instances when you will use one or the other (not the actual steps to apply them).

Subnet Mask:

• When applying an IP to an interface
• Routing protocol summary addresses
• BGP
• PIX security appliance ACL's
• ASA security appliance ACL's
• When creating DHCP pools on a Switch or Router

Wildcard Mask:

• EIGRP network statements
• OSPF network statements
• VPN concentrator network lists (when setting the local and remote allowed networks)
• Router ACL's

This list is not exhaustive and I will add to it as I come across new instances where you use either a Subnet mask or Wildcard mask.