Summary
Distance vector algorithms call for each router to send its entire routing table to each of its adjacent neighbors. The routing tables include information about the total path cost as defined by the metrics and the logical address of the first router on the path to each network contained in the table.
RIP uses many techniques to reduce routing loops and counting to infinity. RIP permits a maximum hop count of 15. A destination greater than 15 hops away is tagged as unreachable.
The split horizon rule specifies that it is not useful to send information about a route back in the direction from which it came. In some network configurations, it may be necessary to disable split horizon.
Route poisoning is used to overcome large routing loops and provide information when a network is down. It also keeps a router from receiving incorrect updates.
Holddown timers help prevent counting to infinity but also increase convergence time. The default holddown for RIP is 180 seconds. Triggered updates are also sent if routing information changes. The router sends triggered routing update on its other interfaces rather than waiting on the routing update timer to expire.
RIP v2 enhancements include the ability to carry additional packet routing information, an authentication mechanism to secure table updates, and support for VLSM. By default, routing updates are broadcast every 30 seconds.
RIP is enabled with the router rip command. The network command is then used to tell the router on which interfaces to run RIP.
A supernet route is a route that covers a greater range of subnets with a single entry. The ip classless global configuration command is used to forward packets to the best supernet route when a router receives packets destined for an unknown subnet of a network.
The two most common commands used to verify that RIP is properly configured are the show ip route and show ip protocols commands. The show ip route command shows the routes that are installed in the routing table and the status of each route. The show ip protocols command is used to verify the state of the active routing protocol as well as the installed routes specific to the protocol.
To display RIP routing updates as they are sent and received, use the debug ip rip command.
The passive-interface command prevents routers from sending routing updates through a router interface. This keeps update messages from being sent through a router interface so that other systems on a network will not learn about routes dynamically.
The show ip route command is used to find equal cost routes for load balancing. RIP uses round robin load balancing. Routers take turns to forward packets over equal cost paths. IGRP is a distance vector routing protocol that measures distances to mathematically compare routes. It sends routing updates at 90 second intervals to advertise networks for an AS. IGRP uses a composite metric. This metric is calculated as a function of bandwidth, delay, load, and reliability. IGRP advertises three types of routes. These include interior, system, and exterior. There are many features such as holddowns and split horizons that provide stability. Use the show ip protocols and the show ip route commands to verify that IGRP is properly configured. In addition, the ping and trace commands are used to troubleshoot errors.
This page summarizes the topics discussed in this module.
Distance vector algorithms call for each router to send its entire routing table to each of its adjacent neighbors. The routing tables include information about the total path cost as defined by the metrics and the logical address of the first router on the path to each network contained in the table.
RIP uses many techniques to reduce routing loops and counting to infinity. RIP permits a maximum hop count of 15. A destination greater than 15 hops away is tagged as unreachable.
The split horizon rule specifies that it is not useful to send information about a route back in the direction from which it came. In some network configurations, it may be necessary to disable split horizon.
Route poisoning is used to overcome large routing loops and provide information when a network is down. It also keeps a router from receiving incorrect updates.
Holddown timers help prevent counting to infinity but also increase convergence time. The default holddown for RIP is 180 seconds. Triggered updates are also sent if routing information changes. The router sends triggered routing update on its other interfaces rather than waiting on the routing update timer to expire.
RIP v2 enhancements include the ability to carry additional packet routing information, an authentication mechanism to secure table updates, and support for VLSM. By default, routing updates are broadcast every 30 seconds.
RIP is enabled with the router rip command. The network command is then used to tell the router on which interfaces to run RIP.
A supernet route is a route that covers a greater range of subnets with a single entry. The ip classless global configuration command is used to forward packets to the best supernet route when a router receives packets destined for an unknown subnet of a network.
The two most common commands used to verify that RIP is properly configured are the show ip route and show ip protocols commands. The show ip route command shows the routes that are installed in the routing table and the status of each route. The show ip protocols command is used to verify the state of the active routing protocol as well as the installed routes specific to the protocol.
To display RIP routing updates as they are sent and received, use the debug ip rip command.
The passive-interface command prevents routers from sending routing updates through a router interface. This keeps update messages from being sent through a router interface so that other systems on a network will not learn about routes dynamically.
The show ip route command is used to find equal cost routes for load balancing. RIP uses round robin load balancing. Routers take turns to forward packets over equal cost paths. IGRP is a distance vector routing protocol that measures distances to mathematically compare routes. It sends routing updates at 90 second intervals to advertise networks for an AS. IGRP uses a composite metric. This metric is calculated as a function of bandwidth, delay, load, and reliability. IGRP advertises three types of routes. These include interior, system, and exterior. There are many features such as holddowns and split horizons that provide stability. Use the show ip protocols and the show ip route commands to verify that IGRP is properly configured. In addition, the ping and trace commands are used to troubleshoot errors.
Comments
Post a Comment