Common RIP configuration issues 7.2.4 This page will provide some more information about the methods that are used to reduce routing loops. RIP routers must rely on neighbor routers for some types of network information. A common term used to describe this functionality is Routing by Rumor. RIP uses a distance vector routing algorithm. All distance vector routing protocols have issues that are primarily created by slow convergence. Convergence is when all routers in a network have the same routing information. Among these issues are routing loops and counting to infinity. These result in inconsistencies due to update messages with incorrect routes that are propagated around the network. To reduce routing loops and counting to infinity, RIP uses the following techniques: Split horizon Poison reverse Holddown counters Triggered updates Some of these methods may need to be configured. RIP permits a maximum hop count of 15. Any destination greater that 15 hops away ...
Posts
Using the ip classless command 7.2.3 This page will explain what the ip classless command is and how it is used. Sometimes a router receives packets destined for an unknown subnet of a network that has directly connected subnets. Use the ip classless global configuration command to instruct the Cisco IOS software to forward these packets to the best supernet route. A supernet route is a route that covers a greater range of subnets with a single entry. For example, if an enterprise uses the entire subnet 10.10.0.0 /16, then a supernet route for 10.10.10.0 /24 would be 10.10.0.0 /16. The ip classless command is enabled by default in Cisco IOS Software Release 11.3 and later. To disable this feature, use the no form of this command. When this feature is disabled any packets received that are destined for a subnet that falls within the subnetwork addressing scheme of the router will be discarded. IP classless only affects the operation of the forwarding processes in IOS. IP ...
RIP Configuring 7.2.2 This page will explain how RIP is configured. The router rip command enables RIP as the routing protocol. The network command is then used to tell the router on which interfaces to run RIP. The routing process associates specific interfaces with the network addresses and begins to send and receive RIP updates on these interfaces. RIP sends routing-update messages at regular intervals. When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route. The received metric value for the path is increased by 1, and the source interface of the update is indicated as the next hop in the routing table. RIP routers maintain only the best route to a destination but can maintain multiple equal-cost paths to the destination. Most routing protocols use a combination of time-driven and event-driven updates. RIP is time-driven, but the Cisco implementation of RIP sends triggered updates whenever a change is...
RIP RIP routing process 7.2.1 This page will provide an overview of the RIP routing process. The modern open standard version of RIP, which is sometimes referred to as IP RIP, is formally detailed in two separate documents. The first is known as Request for Comments (RFC) 1058 and the other as Internet Standard (STD) 56. RIP has evolved over the years from a Classful Routing Protocol, RIP Version 1 (RIP v1), to a Classless Routing Protocol, RIP Version 2 (RIP v2). RIP v2 enhancements include the following: Ability to carry additional packet routing information Authentication mechanism to secure table updates Support for variable-length subnet mask (VLSM) To prevent indefinite routing loops, RIP implements a limit on the number of hops allowed in a path from a source to a destination. The maximum number of hops in a path is 15. When a router receives a routing update that contains a new or changed entry, the metric value is increased by 1 to account fo...