Question

Answer the following questions related to Access Control Lists (ACLs):

1. Why do we require access list?
2. What is difference between standard access lists and extended?
3. What is difference between ACL and firewall?

Answer 1

Standard Access List Extended Access List The access-list number range is 1 - 99 • The access-list number range is 100 - 199 Can block a Network, Host, Subnet and Service • Can block a Network, Host and Subnet • Two way communication is stopped • One way communication is stopped • All services are blocked. • Selected services can be blocked. Implemented closest to the destination. • Implemented closest to the source. • Filtering is done based on only source IP address • Checks source, destination, protocol, port no

Access Control List • ACL is a set of rules which will allow or deny the specific traffic moving through the router • It is a Layer 3 security which controls the flow of traffic from one router to another. • It is also called as Packet Filtering Firewall.

ACLs and Firewall Routers Border routers are charged with providing network security from potential attacks from outside the network. The figure shows the simplest situation where the border router becomes the clear demarcation between the network and the rest of the world. Typically intruders come from the global Internet and the thousands of networks connected to it. External Internal so Internet Local network

ACLs and Firewall Routers Another type of firewall implementation uses two or more routers to provide the security. The border router, A, is ultimately responsible for securing the LAN(s). The firewall router, F, is responsible for protecting both the shared servers and the internal networks from attack from outside. In an optimal solution, this would be a specialty device like Cisco's PIX box, which combines hardware and software to secure the connection. Whether a specialty device or a router with the firewall feature set, ACLs will be a part of the solution. DMZ Internet SO SO LAN 2 LAN 1 Shared servers