ACL Fundamentals

Hello Friends!!!
ACL stands for ACL-Access Control List, list of statements which matched with packets and check condition for allow or block packets towards destination.

Types Of ACL : Standard & Extended ACL

Standard ACL check only source address of packet and take decision it could not check whatever destination and which applications (port no).

Extended ACL check source address, destination address, protocol, and port numbers.

Number Allocated to ACLs: (1) Standard ACL (0-99, 1300-1999)
(2) Extended ACL (100-199, 2000-2699)


Before Implementing ACL on routers we have to clear about inbound and outbound interface:

Inbound: check packet before entering packets
Inbound method apply on interface then we first check packet before packet goes to routing!!! easy...

Outbound: check packet before leaving interface
Outbound method apply on interface then first go to routing table check route and check ACL for allow or deny.

Wildcard Mask: Reverse of Subnet mask in we match and don't match of bits. Here 0 means must match and 1's means don't match.
e.g 10.23.23.0 0.0.0.255 means first three octant matched last one not required.

For more detail and implementaion I put blog in next blog..

Thank You,

Regards
Jignesh