As I discuss the Access Control List (ACLs) in my previous articles that it is a technique used for monitoring outgoing traffic as well as incoming traffic and allowing them to pass or deny based on the source IP address, destination IP addresses, service protocols and ports. The rules give control for packets that enter the router, packets that relay through the router and packet that exit from the router interface. ACLs do not act on the packets originating from the router itself. We can configure and apply ACL operation to inbound and or outbound direction:-
In this type of Access Control Lists (ACLs) analyze incoming packets before routing to the outbound interface. An inbound Access Control Lists (ACL) is efficient because it reduce the load of routing lookups. If packet not matched to the criteria; It is discarded before routing table lookup. If ACL permit the packet for outbound then router processed it for routing. Inbound ACLs are specially perfect to filter packets when only single inbound interface is the source of the packets.
In this type of ACLs the router receives incoming packets and route the packets to outbound interface. After route lookup, they are processed through the outbound ACL to exit interface. It is best when packets coming; from multiple inbound interfaces and the same filter required all incoming traffic before exiting the same outbound interface.
The end statement for both inbound and outbound ACLs; are always an implicit deny which automatically inserted at the end of each ACL. The implicit deny blocks all type of traffic because of implicit deny. The figure below illustrates inbound and outbound access control list (ACLs).
There are several advantages and disadvantages of link-state routing protocols compared to distance vector routing protocols. In this article, we are going to discuss the advantages and disadvantages of a link-state routing protocol. Advantages of link-state Fast Network Convergence– Fast network convergence is the main advantage of the link-state routing protocol. Because on receiving an […]
The routers in the same area use the link-state database and SPF algorithm to build the SPF tree. For example, in the figure below R1 build the SPF tree using the link-state information from all other routers. To start, the SPF algorithm read the router’s LSP to recognize networks and also the costs of the […]
After building the LSP each router flood the LSP to all neighbors in the link-state routing process. This is the fourth in step link-state routing process. The neighbor routers receive the LSP and save it in the database. All routers in the same routing area flood the link-state information to each other. When a router […]
The third step in the link-state routing process is the building of the link-state packet (LSP) containing the state of each directly connected link. It carries the information generated by a network router in a link state routing protocol lists the router’s neighbors. It is a special datagram determining the names of routers including; the cost or distance to any […]
The second step in the link-state routing process is the responsibility of meeting with neighbors on directly connected networks. Routers with link-state routing protocol use a Hello protocol for establishing and maintaining router neighbor relationships. A neighbor is any other router enabled with the same link-state routing protocol. The link-state routing protocol uses Hello, packets […]
Link and Link-state is the first step in the routing process. Each router learns about its own links and directly connected networks. When a router interface is configured with an IP address and subnet mask and also in the state of no shutdown, then it becomes part of that network. Refer to the topology in […]
Link state routing protocols are also known as shortest path first protocol. It maintains a complete picture of all the router running a link state routing protocol in the complete network. All routers running a link state routing protocol originates information of itself and its directly connected routers, links, and the state of those links […]
Shortest path first protocol also known as Link-state routing protocols using Edsger Dijkstra’s shortest path first (SPF) algorithm. Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS) the two commonly used link-state routing protocols. Link-state routing protocols have more complex than the distance vector routing protocol. But, the basic functionality and configuration of link-state […]