Managing Traffic with Access Control Lists

To classify the IP packets, standard and extended Cisco IOS access control lists (ACLs) are used. And by using ACLs, various features can be applied, mainly as dial on demand routing (DDR), policy-based routing, encryption, quality of service (QoS), Port Address Translation, and the Network Address Translation (NAT), are the packets classified.

Access Control List Operation:

To know how to determine and implement on the Cisco network and systems there should be through understanding on the access control lists (ACL). Filter packets and the security feature on the inbound and the outbound router interfaces will be provided by the access control operation.

 

Understanding the ACLs:

ACLs are primarily used in Cisco devices by two main functions they are filtering and the classification and they are explained as below:

• Filtering:

In the increase router connection around the network the increase of internet all over the globe randomly increases the new sort of challenges are occurred. The network administrators face a various problems and they have a dilemma of how to terminate the unwanted traffic and allow clear access to the appropriate users. And for example data can be filtered from the rest of the network from accessing the important and sensitive data from the finance subnet using the ACL as a filter.

• Classification:

ACLs are used in the router to identify the traffic control. Traffic was identified and classified by the ACL the router can be configured to know and to handle the traffic. And by considering the example the ACL is identified in the certain subnet and the priority is given by the ACL over different types in the congested WAN link.

Using the ACLs in the filtering and the classification they provide a powerful toolset in the Cisco IOS. Various ACLs, administration uses the tools to block the traffic from the internet at which will provide an over controlled access to manage the Cisco IOS devices and which provides the address translation for the private address such as the 192.168.0.0 network.

Cisco have the whole access and it will deny or permit the ACLs following points:

• Ports of the router administration telnet traffic into or out of the router.
• The packets are used to the crossing from the various specified router interfaces and the traffic which was going along the Router.

In the traffic the IP is permitted in and out at all the various interfaces by default.

When the packets are discard by the router then, a packet is reached to the sender notifying the destination was not reached. “Destination unreachable (U.U.U.)”is a discard result shown by ACLs in an IP protocol. And in a trace route “Administratively prohibited (! A *! A)” is sent in a response of the ping.

Differentiate in the traffic can be classified in the IP ACLs. Specially defined traffic in the ACL is enabled and assign to the special handling such as.

• To identify the type of the traffic which has to be encrypted in the Virtual Private Network (VPN) connection.
• The address to be translated are identified by using the Network Address Translation (NAT)
• The traffic across the routed in a designated link is use of policy-based routing to identify the designated link.
• Rotes that are required and distributed form one routing protocol to another can be identified. 
•  During the time of congestion they will schedule in a queue that which packet is required to assign with a quality of service (QoS).