Configure RIP Network Optimization

Configuration Condition

Before configuring RIP network optimization, ensure that:

• Interface IP addresses have been configured so that neighbor nodes are reachable at the network layer.
• RIP is enabled.

Configure RIP Timers

RIP does not maintain neighbor relations and it does not support route withdrawn; therefore, the protocol provides four configurable timers to control the network convergence speed. The four timers are: route update timer, router timeout timer, route dampening update timer, and route clear timer.

The route timeout time must be at least three times of the route update time. If no route update packet is received within the route timeout time, the route becomes invalid and it enters a dampening cycle. The length of the dampening cycle is determined by the dampening update time. During the cycle, the route will not be cleared. After the dampening cycle is completed, the route enters the clear cycle. During the cycle, the route can be updated. However, if no route update packet is received during the cycle, the route will be deleted.

Table 5-16 Configuring RIP Timers

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  In the same RIP routing domain, the timer basic configurations on all the devices must be the same to prevent network flapping.

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Configure RIP Split Horizon and Toxicity Reverse of RIP

Split horizon and toxicity reverse are mechanisms that are used to prevent route loops.

1. Configure split horizon.

RIP does not advertise routes that it has learnt from an interface to the interface, preventing routing loops.

Table 5-17 Configuring RIP Split Horizon

2. Configure toxicity reverse.

RIP announces routes that have been learnt from an interface to the interface, but the route metric is the maximum number of hops, 16, preventing routing loops.

Table 5-18 Configuring RIP Toxicity Reverse

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  The split horizon and toxicity reverse functions are valid only for the learnt routes, direct routes in the network covered by RIP, and the redistributed direct and static routes.
• The split horizon function and the toxicity reversion function cannot be used at the same time.

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Configure RIP Source Address Check

Through source address check, RIP checks the source addresses of the received packets. RIP processes only the packets whose source addresses meet the requirements. The check items include: the packet source address is in the same network segment as the input interface address; the packet source address matches the peer end address of the Point-to-Point (P2P) interface.

By default, RIP is enabled to check whether the source addresses received through the Ethernet port are in the same network segment as the address of the interface, and this function cannot be cancelled.

Table 5-19 Configuring RIP Source Address Check

Configure a Static RIP Neighbor

RIP does not maintain neighbor relations, so it does not have the concept of neighbor. Here the neighbor refers to the neighbor RIP routing device. After a static RIP neighbor is specified, RIP sends RIP packets to the neighbor in unicast mode. The configuration is applied to a network that does not support broadcast or multicast, such as point-to-point links. If the configuration is applied to a broadcast or multicast network, it may cause repeated RIP packets in the network.

Table 5-20 Configuring a Static RIP Neighbor

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  RIP advertises routes only to the interfaces that it covers, and the passive interface setting cannot prevent an interface from sending packets to its static neighbor.

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Configure a Passive RIP Interface

To decrease the network bandwidth consumed by the routing protocol, the dynamic routing protocol uses the passive interface function. RIP receives only route update packets on a passive interface, and it does not send route update packets on the passive interface. In a low-speed network with small bandwidth, the passive interface function and the neighbor function cooperate to effectively reduce interactions of RIP routes.

Table 5-21 Configuring a Passive RIP Interface

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  The passive interface function does not restrain an interface from sending unicast route updates to its neighbor devices. When the passive interface function is used with the neighbor command, the function does not restrain an interface from sending unicast route updates to its neighbor devices. This application mode controls a router so that it sends route updates only to some neighbor devices in unicast mode instead of sending route updates to all neighbor devices in broadcast mode (or multicast mode in the case of RIPv2).

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Configure RIP to Trigger Updates

After a device receives an RIP update packet, to reduce the possibility of introducing loops owning to routing table differences, the device advertises the update packet of the route to its neighbor devices immediately instead of waiting for the update timer to time out before an update. The update trigger mechanism speeds up network convergence.

Table 5-22 Configuring RIP to Trigger Updates

Configure an RIP Standby Interface

To speed up backup route convergence, RIP newly supports a backup interface (standby interface) function. On the main route interface of RIP, specify a backup interface for the main interface. In a specific application environment, RIP learns RIP routes only from one line, and the backup line does not provide routing information interaction. If the main interface gets offline, RIP sends Request packets to the peer end through the backup interface periodically (Default: 1s) to request for all routes. If the backup interface receives a Response packet from the peer route, RIP cancels sending of Request packets. It updates the local routing table, and advertises the local routing table to the backup interface. If the backup interface fails to receive a Response packet from the peer end before timeout, RIP cancels sending of Request packets.

Table 5-23 Configuring an RIP Backup Interface.