A special category involves the hybrid routing protocols that feature the best attributes of distance vector and link-state technologies. Link-state routing protocols were developed after distance vector routing protocols and they are much more sophisticated. An important aspect that must be considered when selecting the routing protocol is the difference between distance vector and link-state routing protocols. Interior routing protocols are configured on groups of routers from the same AS thus, the routing activity never leaves the organization’s premises.įigure 1 above illustrates the different routing protocols available. Each routing protocol type will be covered in detail in the following sections, along with their respective design considerations. Interior routing protocols can be further classified as distance vector routing protocols and link-state routing protocols, based on their behavior regarding the router update exchange process. Depending on the zone in which they operate, they can be considered interior (inter-AS) routing protocols or exterior (intra-AS) routing protocols. Routing protocols can be classified based on different criteria. An AS defines a group of network devices under a common administration, and most often this defines a large organization or an ISP. Large networks, including the Internet, are based on the AS concept. Some companies have a very complex and large network infrastructure that spans worldwide, so they use BGP inside their network as their IGRP. The most common EGRP for both IPv4 and IPv6 is the Border Gateway Protocol (BGP). Routing between ASs (from large corporations to the Internet, or between ISPs) is accomplished using special routing protocols called EGRPs. IPv6 uses specially developed versions of routing protocols, such as the following: The most common interior protocols used in non-hub-and-spoke environments are RIPv2, OSPF, IS-IS, and EIGRP. It offers basic routing functionality and works over Cisco Discovery Protocol (CDP). On Demand Routing (ODR) is a Cisco proprietary protocol designed for hub-and-spoke topologies. Note: RIPv1 and IGRP are considered legacy protocols and some modern network devices do not support them. When routing between devices within an organization (Autonomous System – AS), there are many IPv4-based IGRPs to choose from, such as the following: Dynamic RoutingĪn important decision to be made when choosing the routing protocol is whether an Interior Gateway Routing Protocol (IGRP) or an Exterior Gateway Routing Protocol (EGRP) will be needed. Static routing can also be used in the form of floating static routes, for example, setting the Administrative Distance (AD) of a particular static route to a higher (worse) value than the AD value of the same route learned via a routing protocol for failover reasons. Static routes can be used in conjunction with dynamic routing protocols to reach specific networks or to provide the default gateway (e.g., pointing to the ISP), which is useful in situations where the destination network is not part of the routing protocol database.Īnother scenario in which static routes are used is to override some dynamically learned routing information. Static RoutingĮven though static routes may not seem necessary in modern networks, there are situations in which they can offer granular control and optimization of the information learned by the routing protocols. Static routing implies manually defining routes on devices and dynamic routing implies using a dedicated routing protocol that will build the routing table. The first key decision criteria is figuring out whether static or dynamic routing should be used. Network designers should know the key characteristics that different routing protocols have because they will be in a position to recommend specific routing protocols for different projects. Related posts: Concepts of Routing Protocolsīefore analyzing details about each individual routing protocol, some general information about IP routing will be presented first.
0 Comments
Leave a Reply. |