Mga Wildcard Mask sa Cisco IOS: Gabay para sa ACL at OSPF

1. Apa itu Wildcard Mask?

Wildcard mask adalah bitmask 32-bit di Cisco IOS untuk menentukan bit mana yang harus cocok persis (bit 0) dan bit mana yang diabaikan (bit 1).

2. Membalikkan Subnet Mask

Subnet Mask:   255.255.255.0  (/24)
Calculation:   (255-255).(255-255).(255-255).(255-0)
Wildcard Mask: 0.0.0.255

Subnet Mask:   255.255.252.0  (/22)
Calculation:   (255-255).(255-255).(255-252).(255-0)
Wildcard Mask: 0.0.3.255

3. Konfigurasi CLI Cisco

! Interface Configuration
Router(config)# interface GigabitEthernet0/0/1
Router(config-if)# ip address 10.0.50.1 255.255.255.0
Router(config-if)# no shutdown

! OSPF Network Statement with Wildcard Mask
Router(config)# router ospf 1
Router(config-router)# network 10.0.50.0 0.0.0.255 area 0

! Extended ACL Rule
Router(config)# ip access-list extended SECURE_VLAN
Router(config-ext-nacl)# permit ip 10.0.50.0 0.0.0.255 192.168.10.0 0.0.0.255

4. Wildcard Mask Non-Kontigu

Wildcard mask tidak wajib berupa angka biner 1 berurutan. Contoh 0.0.0.254 dapat memfilter seluruh alamat IP bernomor genap.