RIP is a simple Interior Gateway Protocol (IGP), mainly used in small-sized networks, such as academic networks and simple LANs. It is not applicable to complex networks.

RIP is widely used in practical networking because it is easy to implement, configure, and maintain.

RIP working mechanism

Introduction

RIP is a distance vector routing protocol, using UDP packets for exchanging information through port 520.

RIP uses a hop count to measure the distance to a destination. The hop count from a router to a directly connected network is 0. The hop count from a router to a directly connected router is 1. To limit convergence time, the RIP metric value ranges from 0 to 15. A metric value of 16 (or greater) is considered infinite, which means the destination network is unreachable. Because of this, RIP is not suitable for large-sized networks.

RIP prevents routing loops by implementing the split horizon and poison reverse functions.

RIP routing table

A RIP router has a routing table containing routing entries of all reachable destinations, and each routing entry contains the following elements:

· Destination address—IP address of a host or a network

· Next hop—IP address of the adjacent router’s interface to reach the destination

· Egress interface—Packet outgoing interface

· Metric—Cost from the local router to the destination

· Route time—Time elapsed since the routing entry was last updated. The time is reset to 0 every time the routing entry is updated.

· Route tag—Identifies a route, used in a routing policy to flexibly control routes.

RIP timers

RIP employs the following timers—update, timeout, suppress, and garbage-collect.

· The update timer defines the interval between routing updates.

· The timeout timer defines the route aging time. If no update for a route is received within the aging time, the metric of the route is set to 16 in the routing table.

· The suppress timer defines how long a RIP route stays in the suppressed state. When the metric of a route is 16, the route enters the suppressed state. In the suppressed state, only routes which come from the same neighbor and whose metric is less than 16 will be received by the router to replace unreachable routes.

· The garbage-collect timer defines the interval from when the metric of a route becomes 16 to when it is deleted from the routing table. During the garbage-collect timer length, RIP advertises the route with the routing metric set to 16. If no update is announced for that route after the garbage-collect timer expires, the route will be deleted from the routing table.

Routing loops prevention

RIP is a distance vector (D-V) routing protocol. Since a RIP router advertises its own routing table to neighbors, routing loops may occur.

RIP uses the following mechanisms to prevent routing loops:

· Counting to infinity—The metric value of 16 is defined as unreachable. When a routing loop occurs, the metric value of the route will increment to 16.

· Split horizon—A router does not send the routing information learned from a neighbor to the neighbor to prevent routing loops and save bandwidth.

· Poison reverse—A router sets the metric of routes received from a neighbor to 16 and sends back these routes to the neighbor to help delete such information from the neighbor’s routing table.

· Triggered updates—A router advertises updates once the metric of a route is changed rather than after the update period expires to speed up network convergence.

Operation of RIP

The following procedure describes how RIP works.

1. After RIP is enabled, the router sends request messages to neighboring routers. Neighboring routers return Response messages including information about their routing tables.

2. After receiving this information, the router updates its local routing table, and sends triggered update messages to its neighbors. All routers on the network do this to keep the latest routing information.

3. By default, a RIP router sends its routing table to neighbors every 30 seconds.

4. RIP ages out routes by adopting an aging mechanism to keep only valid routes.

RIP version

RIP has the following versions: RIPv1 and RIPv2.

RIPv1, a classful routing protocol, supports message advertisement via broadcast only. RIPv1 protocol messages do not carry mask information, which means it can only recognize routing information of natural networks such as Class A, B, and C. That is why RIPv1 does not support discontiguous subnets.

RIPv2 is a classless routing protocol, and has the following advantages over RIPv1.

· Supports route tags. Route tags are used in routing policies to flexibly control routes.

· Supports masks, route summarization and Classless Inter-Domain Routing (CIDR).

· Supports designated next hops to select the best ones on broadcast networks.

· Supports multicasting routing updates to reduce resource consumption. Only RIPv2 routers can receive these update messages.

· Supports plain text authentication and MD5 authentication to enhance security.

NOTE:

RIPv2 has two types of message transmission: broadcast and multicast. Multicast is the default type using 224.0.0.9 as the multicast address. The interface working in the RIPv2 broadcast mode can also receive RIPv1 messages.

RIP message format

A RIP message consists of a header and up to 25 route entries. (A RIPv2 authentication message uses the first route entry as the authentication entry, leaving 24 available.)

RIPv1 message format

Figure 1 RIPv1 Message Format

Header description:

· Command—Type of message. 1 indicates request, which is used to request all or part of the routing information from the neighbor; 2 indicates response, which contains all or part of the routing information. A response message consists of up to 25 route entries.

· Version—Version of RIP, 0x01 for RIPv1.

· Must be zero—This field must be zero

· AFI—Address Family Identifier, 2 for IP.

· IP Address—Destination IP address of the route. It can be a natural network, subnet or a host address.

· Metric—Cost of the route

RIPv2 message format

The format of RIPv2 message is similar to RIPv1.

Figure 2 RIPv2 Message Format

Differences from RIPv1:

· Version–Version of RIP. For RIPv2 the value is 0x02.

· Route tag

· IP address—Destination IP address. It can be a natural network address, subnet address or host address.

· Subnet mask—Mask of the destination address

· Next hop—If set to 0.0.0.0, it indicates that the originator of the route is the best next hop. Otherwise it indicates a next hop better than the originator of the route.

RIPv2 authentication message format

RIPv2 sets the AFI field of the first route entry to 0xFFFF to identify authentication information. See Figure 3.

Figure 3 RIPv2 Authentication Message

· Authentication Type—A value of 2 represents plain text authentication; a value of 3 represents MD5.

· Authentication—Authentication data, including password information when plain text authentication is adopted or including key ID, MD5 authentication data length and sequence number when MD5 authentication is adopted.

NOTE:

· RFC 1723 only defines plain text authentication. For more information about MD5 authentication, see RFC 2453, RIP Version 2.

· With RIPv1, you can configure the authentication mode in interface view. However, the configuration will not take effect because RIPv1 does not support authentication.

Protocols and standards

· RFC 1058, Routing Information Protocol

· RFC 1723, RIP Version 2 - Carrying Additional Information

· RFC 1721, RIP Version 2 Protocol Analysis

· RFC 1722, RIP Version 2 Protocol Applicability Statement

· RFC 1724, RIP Version 2 MIB Extension

· RFC 2082, RIPv2 MD5 Authentication

· RFC 2453, RIP Version 2

RIP configuration task list

Complete the following tasks to configure RIP:

Task		Remarks
Configuring RIP basic functions		Required
Configuring RIP route control	Configuring an additional routing metric	Optional
	Configuring RIPv2 route summarization	Optional
	Disabling host route reception	Optional
	Advertising a default route	Optional
	Configuring inbound/outbound route filtering	Optional
	Configuring a priority for RIP	Optional
	Configuring RIP route redistribution	Optional
Tuning and optimizing RIP networks	Configuring RIP timers	Optional
	Configuring split horizon and poison reverse	Optional
	Configuring the maximum number of load balanced routes	Optional
	Enabling zero field check on incoming RIPv1 messages	Optional
	Enabling source IP address check on incoming RIP updates	Optional
	Configuring RIPv2 message authentication	Optional
	Specifying a RIP neighbor	Optional
	Configuring RIP-to-MIB binding	Optional
	Configuring the RIP packet sending rate	Optional

Configuring RIP basic functions

Configuration prerequisites

Before configuring RIP basic functions, complete the following tasks:

· Configure the link layer protocol

· Configure an IP address on each interface, and make sure all adjacent routers are reachable to each other

Configuration procedure

Enabling RIP and a RIP interface

Follow these steps to enable RIP:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enable a RIP process and enter RIP view	rip [ process-id ]	Required Disabled by default
Enable RIP on the interface attached to the specified network	network network-address	Required Disabled by default

NOTE:

· If you make some RIP configurations in interface view before enabling RIP, those configurations will take effect after RIP is enabled.

· RIP runs only on the interfaces residing on the specified networks. Specify the network after enabling RIP to validate RIP on a specific interface.

· You can enable RIP on all interfaces using the command network 0.0.0.0.

· If a physical interface is attached to multiple networks, you cannot advertise these networks in different RIP processes.

Configuring the interface behavior

Follow these steps to configure the interface behavior:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Disable an or all interfaces from sending routing updates (the interfaces can still receive updates)	silent-interface { interface-type interface-number \| all }	Optional All interfaces can send routing updates by default.
Return to system view	quit	—
Enter interface view	interface interface-type interface-number	—
Enable the interface to receive RIP messages	rip input	Optional Enabled by default
Enable the interface to send RIP messages	rip output	Optional Enabled by default

Configuring a RIP version

You can configure a RIP version in RIP or interface view.

· If neither global nor interface RIP version is configured, the interface sends RIPv1 broadcasts and can receive the following packets: RIPv1 broadcast, RIPv1 unicast, RIPv2 broadcast, RIPv2 multicast, and RIPv2 unicast.

· If an interface has no RIP version configured, it uses the global RIP version; otherwise it uses the RIP version configured on it.

· With RIPv1 configured, an interface sends RIPv1 broadcasts, and can receive RIPv1 broadcasts and RIPv1 unicasts.

· With RIPv2 configured, a multicast interface sends RIPv2 multicasts and can receive RIPv2 unicasts, broadcasts, and multicasts.

· With RIPv2 configured, a broadcast interface sends RIPv2 broadcasts and can receive RIPv1 unicasts and broadcasts, and RIPv2 broadcasts, multicasts, and unicasts.

Follow these steps to configure a RIP version:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Specify a global RIP version	version { 1 \| 2 }	Optional By default, if an interface has a RIP version specified, the version takes precedence over the global one. If no RIP version is specified for an interface, the interface can send RIPv1 broadcasts, and receive RIPv1 broadcasts and unicasts, and RIPv2 broadcasts, multicasts, and unicasts.
Return to system view	quit	—
Enter interface view	interface interface-type interface-number	—
Specify a RIP version for the interface	rip version { 1 \| 2 [ broadcast \| multicast ] }	Optional By default, if an interface has no RIP version specified, the global version takes effect. If no global RIP version is specified, the interface can send RIPv1 broadcasts, and receive RIPv1 broadcasts and unicasts, and RIPv2 broadcasts, multicasts, and unicasts.

Configuring RIP route control

In complex networks, you need to configure advanced RIP features.

This section covers the following topics:

· Configuring an additional routing metric

· Configuring RIPv2 route summarization

· Disabling host route reception

· Advertising a default route

· Configuring inbound/outbound route filtering

· Configuring a priority for RIP

· Configuring RIP route redistribution

Before configuring RIP routing feature, complete the following tasks:

· Configure an IP address for each interface, and make sure all neighboring routers can communicate with each other.

· Configure RIP basic functions

Configuring an additional routing metric

An additional routing metric (hop count) can be added to the metric of an inbound or outbound RIP route.

The outbound additional metric is added to the metric of a sent route, and the route’s metric in the routing table is not changed.

The inbound additional metric is added to the metric of a received route before the route is added into the routing table, and the route’s metric is changed. If the sum of the additional metric and the original metric is greater than 16, the metric of the route will be 16.

Follow these steps to configure additional routing metrics:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter interface view	interface interface-type interface-number	—
Define an inbound additional routing metric	rip metricin [ route-policy route-policy-name ] value	Optional 0 by default
Define an outbound additional routing metric	rip metricout [ route-policy route-policy-name ] value	Optional 1 by default

Configuring RIPv2 route summarization

Route summarization means that subnets in a natural network are summarized into a natural network that is sent to other networks. This feature can reduce the size of routing tables.

After route summarization, the smallest metric among all the summarized routes is used as the metric of the summary route.

Enabling RIPv2 route automatic summarization

You can disable RIPv2 route automatic summarization if you want to advertise all subnet routes.

Follow these steps to enable RIPv2 route automatic summarization:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Enable RIPv2 automatic route summarization	summary	Optional Enabled by default If the subnet routes in the routing table are not consecutive, disable automatic route summarization to avoid black hole routing.

Advertising a summary route

Follow these steps to configure RIPv2 to advertise a summary route on the specified interface:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Disable RIPv2 automatic route summarization	undo summary	Required Enabled by default
Return to system view	quit	—
Enter interface view	interface interface-type interface-number	—
Advertise a summary route	rip summary-address ip-address { mask \| mask-length }	Required

NOTE:

You need to disable RIPv2 route automatic summarization before advertising a summary route on an interface.

Disabling host route reception

Sometimes a router may receive from the same network many host routes, which are not helpful for routing and consume a large amount of network resources. You can disable RIP from receiving host routes to save network resources.

Follow these steps to disable RIP from receiving host routes:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Disable RIP from receiving host routes	undo host-route	Required Enabled by default

NOTE:

RIPv2 can be disabled from receiving host routes, but RIPv1 cannot.

Advertising a default route

You can configure RIP to advertise a default route with a specified metric to RIP neighbors.

· In RIP view, you can configure all the interfaces of the RIP process to advertise a default route; in interface view, you can configure a RIP interface of the RIP process to advertise a default route. The interface view takes precedence over on the interface.

· If a RIP process is enabled to advertise a default route, to disable an interface of the RIP process from default route advertisement, you can use the rip default-route no-originate command on the interface.

Follow these steps to configure RIP to advertise a default route:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Enable RIP to advertise a default route	default-route { only \| originate } [ cost cost ]	Optional Not enabled by default
Return to system view	quit	—
Enter interface view	interface interface-type interface-number	—
Configure the RIP interface to advertise a default route	rip default-route { { only \| originate } [ cost cost ] \| no-originate }	Optional By default, a RIP interface can advertise a default route if the RIP process is configured with default route advertisement.

NOTE:

The router enabled to advertise a default route does not receive default routes from RIP neighbors.

Configuring inbound/outbound route filtering

The device supports route filtering. You can filter routes by configuring the inbound and outbound route filtering policies by referencing an ACL or IP prefix list. You can also configure the router to receive only routes from a specified neighbor.

Follow these steps to configure route filtering:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Configure the filtering of incoming routes	filter-policy { acl-number \| gateway ip-prefix-name \| ip-prefix ip-prefix-name [ gateway ip-prefix-name ] } import [ interface-type interface-number ]	Required Not configured by default
Configure the filtering of outgoing routes	filter-policy { acl-number \| ip-prefix ip-prefix-name } export [ protocol [ process-id ] \| interface-type interface-number ]	Required Not configured by default

NOTE:

· Using the filter-policy import command filters incoming routes. Routes not passing the filtering will be neither installed into the routing table nor advertised to neighbors.

· Using the filter-policy export command filters outgoing routes, including routes redistributed with the import-route command.

Configuring a priority for RIP

Multiple IGP protocols may run in a router. If you want RIP routes to have a higher priority than those learned by other routing protocols, assign RIP a smaller priority value to influence optimal route selection.

Follow these steps to configure a priority for RIP:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Configure a priority for RIP	preference value	Optional 100 by default

Configuring RIP route redistribution

If a router runs RIP and other routing protocols, you can configure RIP to redistribute static or direct routes.

Follow these steps to configure RIP route redistribution:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Configure a default metric for redistributed routes	default cost value	Optional The default metric of a redistributed route is 0.
Redistribute routes from another protocol	import-route protocol [ process-id \| all-processes ] [ cost cost \| tag tag ] *	Required No redistribution is configured by default.

NOTE:

Only active routes can be redistributed. Use the display ip routing-table protocol command to display route state information.

Tuning and optimizing RIP networks

Complete the following tasks before tuning and optimizing RIP networks:

· Configure network addresses for interfaces, and make neighboring nodes reachable to each other

· Configure RIP basic functions

Configuring RIP timers

You can change the RIP network convergence speed by adjusting RIP timers.

Follow these steps to configure RIP timers:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Configure values for RIP timers	timers { garbage-collect garbage-collect-value \| suppress suppress-value \| timeout timeout-value \| update update-value } *	Optional The default update timer, timeout timer, suppress timer, and garbage-collect timer are 30s, 180s, 120s and 120s respectively.

NOTE:

Based on network performance, you need to make RIP timers of RIP routers identical to each other to avoid unnecessary traffic or route oscillation.

Configuring split horizon and poison reverse

The split horizon and poison reverse functions can prevent routing loops.

If both split horizon and poison reverse are configured, only the poison reverse function takes effect.

Enabling split horizon

Split horizon disables RIP from sending routes through the interface where the routes were learned to prevent routing loops between adjacent routers.

Follow these steps to enable split horizon:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter interface view	interface interface-type interface-number	—
Enable split horizon	rip split-horizon	Optional Enabled by default

Enabling poison reverse

Poison reverse allows RIP to send routes through the interface where the routes were learned, but the metric of these routes is always set to 16 (unreachable) to avoid routing loops between neighbors.

Follow these steps to enable poison reverse:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter interface view	interface interface-type interface-number	—
Enable poison reverse	rip poison-reverse	Required Disabled by default

Configuring the maximum number of load balanced routes

This task allows you to implement load balancing over multiple equal-cost RIP routes.

Follow these steps to configure the maximum number of load balanced routes:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Configure the maximum number of load balanced routes	maximum load-balancing number	Optional 6 by default

Enabling zero field check on incoming RIPv1 messages

Some fields in the RIPv1 message must be zero. These fields are called “zero fields”. You can enable zero field check on received RIPv1 messages. If such a field contains a non-zero value, the RIPv1 message will not be processed. If you are sure that all messages are trusty, disable zero field check to save CPU resources.

This feature does not apply to RIPv2 packets that have no zero fields.

Follow these steps to enable zero field check on incoming RIPv1 messages:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Enable zero field check on received RIPv1 messages	checkzero	Optional Enabled by default

Enabling source IP address check on incoming RIP updates

You can enable source IP address check on incoming RIP updates.

For a message received on an Ethernet interface, RIP compares the source IP address of the message with the IP address of the interface. If they are not in the same network segment, RIP discards the message.

For a message received on a serial interface, RIP checks whether the source address of the message is the IP address of the peer interface. If not, RIP discards the message.

Follow these steps to enable source IP address check on incoming RIP updates:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Enable source IP address check on incoming RIP messages	validate-source-address	Optional Enabled by default

NOTE:

The source IP address check feature should be disabled if the RIP neighbor is not directly connected.

Configuring RIPv2 message authentication

In a network requiring high security, you can configure this task to implement RIPv2 message validity check and authentication.

RIPv2 supports two authentication modes: plain text and MD5.

In plain text authentication, the authentication information is sent with the RIP message; however, this cannot meet high security needs.

Follow these steps to configure RIPv2 message authentication:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter interface view	interface interface-type interface-number	—
Configure RIPv2 authentication	rip authentication-mode { md5 { rfc2082 [ cipher ] key-string key-id \| rfc2453 [ cipher ] key-string } \| simple [ cipher ] password }	Required

NOTE:

This feature does not apply to RIPv1 because RIPv1 does not support authentication. Although you can specify an authentication mode for RIPv1 in interface view, the configuration does not take effect.

Specifying a RIP neighbor

Usually, RIP sends messages to broadcast or multicast addresses. On non broadcast or multicast links, you need to manually specify RIP neighbors.

Follow these steps to specify a RIP neighbor:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIP view	rip [ process-id ]	—
Specify a RIP neighbor	peer ip-address	Required
Disable source address check on incoming RIP updates	undo validate-source-address	Required Not disabled by default

NOTE:

· You need not use the peer ip-address command when the neighbor is directly connected; otherwise the neighbor may receive both the unicast and multicast (or broadcast) of the same routing information.

· If a specified neighbor is not directly connected, you need to disable source address check on incoming updates.

Configuring RIP-to-MIB binding

This task allows you to enable a specific RIP process to receive SNMP requests.

Follow these steps to bind RIP to MIB:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Bind RIP to MIB	rip mib-binding process-id	Optional By default, MIB is bound to RIP process 1.

To do…

Use the command…

Remarks

Enter system view

system-view

—

Bind RIP to MIB

rip mib-binding process-id

Optional

By default, MIB is bound to RIP process 1.

Configuring the RIP packet sending rate

RIP periodically sends routing information in RIP packets to RIP neighbors.

Sending large numbers of RIP packets at the same time may affect device performance and consume large network bandwidth. To solve this problem, you can specify the maximum number of RIP packets that can be sent at the specified interval.

Follow these steps to configure the RIP packet sending rate:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enable a RIP process and enter RIP view	rip [ process-id ]	—
Configure the maximum number of RIP packets that can be sent at the specified interval	output-delay time count count	Optional By default, an interface sends up to three RIP packets every 20 milliseconds.

Displaying and maintaining RIP

To do…	Use the command…	Remarks
Display RIP current status and configuration information	display rip [ process-id ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
Display all active routes in RIP database	display rip process-id database [ \| { begin \| exclude \| include } regular-expression ]
Display RIP interface information	display rip process-id interface [ interface-type interface-number ] [ \| { begin \| exclude \| include } regular-expression ]
Display routing information about a specified RIP process	display rip process-id route [ ip-address { mask \| mask-length } \| peer ip-address \| statistics ] [ \| { begin \| exclude \| include } regular-expression ]
Reset a RIP process	reset rip process-id process	Available in user view
Clear the statistics of a RIP process	reset rip process-id statistics	Available in user view

RIP configuration examples

Configuring RIP version

Network requirements

As shown in Figure 4, enable RIPv2 on all interfaces on Switch A and Switch B.

Figure 4 Network diagram for RIP version configuration

Configuration procedure

1. Configure an IP address for each interface (omitted)

2. Configure basic RIP functions

# Configure Switch A.

[SwitchA] rip

[SwitchA-rip-1] network 192.168.1.0

[SwitchA-rip-1] network 172.16.0.0

[SwitchA-rip-1] network 172.17.0.0

# Configure Switch B.

[SwitchB] rip

[SwitchB-rip-1] network 192.168.1.0

[SwitchB-rip-1] network 10.0.0.0

# Display the RIP routing table of Switch A.

[SwitchA] display rip 1 route

Route Flags: R - RIP, T - TRIP

P - Permanent, A - Aging, S - Suppressed, G - Garbage-collect

----------------------------------------------------------------------------

Peer 192.168.1.2 on Vlan-interface100

Destination/Mask Nexthop Cost Tag Flags Sec

10.0.0.0/8 192.168.1.2 1 0 RA 11

The output shows that RIPv1 uses a natural mask.

3. Configure RIP version

# Configure RIPv2 on Switch A.

[SwitchA] rip

[SwitchA-rip-1] version 2

[SwitchA-rip-1] undo summary

# Configure RIPv2 on Switch B.

[SwitchB] rip

[SwitchB-rip-1] version 2

[SwitchB-rip-1] undo summary

# Display the RIP routing table on Switch A.

[SwitchA] display rip 1 route

Route Flags: R - RIP, T - TRIP

P - Permanent, A - Aging, S - Suppressed, G - Garbage-collect

----------------------------------------------------------------------------

Peer 192.168.1.2 on Vlan-interface100

Destination/Mask Nexthop Cost Tag Flags Sec

10.0.0.0/8 192.168.1.2 1 0 RA 50

10.2.1.0/24 192.168.1.2 1 0 RA 16

10.1.1.0/24 192.168.1.2 1 0 RA 16

The output shows that RIPv2 uses classless subnet mask.

NOTE:

Because RIPv1 routing information has a long aging time, it will still exist until it ages out after RIPv2 is configured.

Configuring RIP route redistribution

Network requirements

As shown in the following figure:

· Two RIP processes are running on Switch B, which communicates with Switch A through RIP 100 and with Switch C through RIP 200.

· Configure route redistribution on Switch B to make RIP 200 redistribute direct routes and routes from RIP 100. Switch C can then learn routes destined for 10.2.1.0/24 and 11.1.1.0/24, and Switch A cannot learn routes destined for 12.3.1.0/24 and 16.4.1.0/24.

· Configure a filtering policy on Switch B to filter out the route 10.2.1.1/24 from RIP 100, making the route not advertised to Switch C.

Figure 5 Network diagram for RIP route redistribution configuration

Configuration procedure

1. Configure an IP address for each interface (Omitted).

2. Configure basic RIP functions.

# Enable RIP 100 and specify RIP version 2 on Switch A.

<SwitchA> system-view

[SwitchA] rip 100

[SwitchA-rip-100] network 10.0.0.0

[SwitchA-rip-100] network 11.0.0.0

[SwitchA-rip-100] version 2

[SwitchA-rip-100] undo summary

[SwitchA-rip-100] quit

# Enable RIP 100 and RIP 200 and specify RIP version 2 on Switch B.

<SwitchB> system-view

[SwitchB] rip 100

[SwitchB-rip-100] network 11.0.0.0

[SwitchB-rip-100] version 2

[SwitchB-rip-100] undo summary

[SwitchB-rip-100] quit

[SwitchB] rip 200

[SwitchB-rip-200] network 12.0.0.0

[SwitchB-rip-200] version 2

[SwitchB-rip-200] undo summary

[SwitchB-rip-200] quit

# Enable RIP 200 and specify RIP version 2 on Switch C.

<SwitchC> system-view

[SwitchC] rip 200

[SwitchC-rip-200] network 12.0.0.0

[SwitchC-rip-200] network 16.0.0.0

[SwitchC-rip-200] version 2

[SwitchC-rip-200] undo summary

# Display the routing table of Switch C.

[SwitchC] display ip routing-table

Routing Tables: Public

Destinations : 6 Routes : 6

Destination/Mask Proto Pre Cost NextHop Interface

12.3.1.0/24 Direct 0 0 12.3.1.2 Vlan200

12.3.1.2/32 Direct 0 0 127.0.0.1 InLoop0

16.4.1.0/24 Direct 0 0 16.4.1.1 Vlan400

16.4.1.1/32 Direct 0 0 127.0.0.1 InLoop0

127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0

127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0

3. Configure route redistribution

# On Switch B, configure RIP 200 to redistribute direct routes and routes from RIP 100.

[SwitchB] rip 200

[SwitchB-rip-200] import-route rip 100

[SwitchB-rip-200] import-route direct

[SwitchB-rip-200] quit

# Display the routing table of Switch C.

[SwitchC] display ip routing-table

Routing Tables: Public

Destinations : 8 Routes : 8

Destination/Mask Proto Pre Cost NextHop Interface

10.2.1.0/24 RIP 100 1 12.3.1.1 Vlan200

11.1.1.0/24 RIP 100 1 12.3.1.1 Vlan200

12.3.1.0/24 Direct 0 0 12.3.1.2 Vlan200

12.3.1.2/32 Direct 0 0 127.0.0.1 InLoop0

16.4.1.0/24 Direct 0 0 16.4.1.1 Vlan400

16.4.1.1/32 Direct 0 0 127.0.0.1 InLoop0

127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0

127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0

4. Configure an filtering policy to filter redistributed routes

# Define ACL 2000 and reference it to a filtering policy to filter routes redistributed from RIP 100 on Switch B, making the route not advertised to Switch C.

[SwitchB] acl number 2000

[SwitchB-acl-basic-2000] rule deny source 10.2.1.1 0.0.0.255

[SwitchB-acl-basic-2000] rule permit

[SwitchB-acl-basic-2000] quit

[SwitchB] rip 200

[SwitchB-rip-200] filter-policy 2000 export rip 100

# Display the routing table of Switch C.

[SwitchC] display ip routing-table

Routing Tables: Public

Destinations : 7 Routes : 7

Destination/Mask Proto Pre Cost NextHop Interface

11.1.1.0/24 RIP 100 1 12.3.1.1 Vlan200

12.3.1.0/24 Direct 0 0 12.3.1.2 Vlan200

12.3.1.2/32 Direct 0 0 127.0.0.1 InLoop0

16.4.1.0/24 Direct 0 0 16.4.1.1 Vlan400

16.4.1.1/32 Direct 0 0 127.0.0.1 InLoop0

127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0

127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0

Configuring an additional metric for a RIP interface

Network requirements

As shown in the following figure:

· RIP is enabled on all the interfaces of Switch A, Switch B, Switch C, Switch D, and Switch E. The switches are interconnected through RIPv2.

· Switch A has two links to Switch D. The link from Switch B to Switch D is more stable than that from Switch C to Switch D. Configure an additional metric for RIP routes received through VLAN-interface 200 on Switch A so that Switch A prefers the 1.1.5.0/24 network learned from Switch B.

Figure 6 Network diagram for RIP interface additional metric configuration

Configuration procedure

1. Configure IP addresses for the interfaces (omitted).

2. Configure RIP basic functions.

# Configure Switch A.

<SwitchA> system-view

[SwitchA] rip 1

[SwitchA-rip-1] network 1.0.0.0

[SwitchA-rip-1] version 2

[SwitchA-rip-1] undo summary

[SwitchA-rip-1] quit

# Configure Switch B.

<SwitchB> system-view

[SwitchB] rip 1

[SwitchB-rip-1] network 1.0.0.0

[SwitchB-rip-1] version 2

[SwitchB-rip-1] undo summary

# Configure Switch C.

<SwitchC> system-view

[SwitchB] rip 1

[SwitchC-rip-1] network 1.0.0.0

[SwitchC-rip-1] version 2

[SwitchC-rip-1] undo summary

# Configure Switch D.

<SwitchD> system-view

[SwitchD] rip 1

[SwitchD-rip-1] network 1.0.0.0

[SwitchD-rip-1] version 2

[SwitchD-rip-1] undo summary

# Configure Switch E.

<SwitchE> system-view

[SwitchE] rip 1

[SwitchE-rip-1] network 1.0.0.0

[SwitchE-rip-1] version 2

[SwitchE-rip-1] undo summary

# Display the IP routing table of Switch A.

[SwitchA] display rip 1 database

1.0.0.0/8, cost 0, ClassfulSumm

1.1.1.0/24, cost 0, nexthop 1.1.1.1, Rip-interface

1.1.2.0/24, cost 0, nexthop 1.1.2.1, Rip-interface

1.1.3.0/24, cost 1, nexthop 1.1.1.2

1.1.4.0/24, cost 1, nexthop 1.1.2.2

1.1.5.0/24, cost 2, nexthop 1.1.1.2

1.1.5.0/24, cost 2, nexthop 1.1.2.2

The output shows that two RIP routes can reach network 1.1.5.0/24. Their next hops are Switch B (1.1.1.2) and Switch C (1.1.2.2) respectively, with the same cost of 2. Switch C is the next hop router to reach network 1.1.4.0/24, with a cost of 1.

3. Configure an additional metric for the RIP interface.

# Configure an additional metric of 3 for VLAN-interface 200 on Switch A.

[SwitchA] interface vlan-interface 200

[SwitchA-Vlan-interface200] rip metricin 3

[SwitchA-Vlan-interface200] display rip 1 database

1.0.0.0/8, cost 0, ClassfulSumm

1.1.1.0/24, cost 0, nexthop 1.1.1.1, Rip-interface

1.1.2.0/24, cost 0, nexthop 1.1.2.1, Rip-interface

1.1.3.0/24, cost 1, nexthop 1.1.1.2

1.1.4.0/24, cost 2, nexthop 1.1.1.2

1.1.5.0/24, cost 2, nexthop 1.1.1.2

The output shows that only one RIP route reaches network 1.1.5.0/24, with the next hop as Switch B (1.1.1.2) and a cost of 2.

Troubleshooting RIP

No RIP updates received

Symptom:

No RIP updates are received when the links work properly.

Analysis:

After enabling RIP, you must use the network command to enable corresponding interfaces. Make sure no interfaces are disabled from handling RIP messages.

If the peer is configured to send multicast messages, the same should be configured on the local end.

Solution:

· Use the display current-configuration command to check RIP configuration

· Use the display rip command to check whether an interface is disabled

Route oscillation occurred

Symptom:

When all links work properly, route oscillation occurs on the RIP network. After displaying the routing table, you might find some routes intermittently appear and disappear in the routing table.

Analysis:

In the RIP network, make sure that all the same timers within the entire network are identical and have logical relationships between them. For example, the timeout timer value should be greater than the update timer value.

Solution:

· Use the display rip command to check the configuration of RIP timers

· Use the timers command to adjust timers properly.

03-Layer 3 Configuration Guide

RIP overview

RIP working mechanism

Introduction

RIP routing table

Routing loops prevention

RIP version

RIP message format

RIPv1 message format

RIPv2 message format

RIPv2 authentication message format

Configuring RIP basic functions

Configuration procedure

Enabling RIP and a RIP interface

Configuring the interface behavior

Configuring a RIP version

Configuring RIP route control

Configuring an additional routing metric

Configuring RIPv2 route summarization

Enabling RIPv2 route automatic summarization

Advertising a summary route

Disabling host route reception

Configuring inbound/outbound route filtering

Configuring a priority for RIP

Configuring RIP route redistribution

Tuning and optimizing RIP networks

Configuring RIP timers

Configuring split horizon and poison reverse

Enabling split horizon

Enabling poison reverse

Configuring the maximum number of load balanced routes

Enabling zero field check on incoming RIPv1 messages

Enabling source IP address check on incoming RIP updates

Specifying a RIP neighbor

Configuring RIP-to-MIB binding

RIP configuration examples

Network requirements

Configuration procedure

Configuring RIP route redistribution

Network requirements

Configuration procedure

Configuring an additional metric for a RIP interface

Network requirements

Configuration procedure

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