RIPng uses a hop count to measure the distance to a destination. The hop count is the metric or cost. The hop count from a router to a directly connected network is 0. The hop count between two directly connected routers is 1. When the hop count is greater than or equal to 16, the destination network or host is unreachable.

By default, the routing update is sent every 30 seconds. If the router receives no routing updates from a neighbor within 180 seconds, the routes learned from the neighbor are considered unreachable. If no routing update is received within another 240 seconds, the router removes these routes from the routing table.

RIPng supports split horizon and poison reverse to prevent routing loops and route redistribution.

Each RIPng router maintains a routing database, which includes route entries of all reachable destinations. A route entry contains the following information:

· Destination address—IPv6 address of a host or a network.

· Next hop address—IPv6 address of a neighbor along the path to the destination

· Egress interface—Outbound interface that forwards IPv6 packets

· Metric—Cost from the local router to the destination

· Route time—Time that elapsed since a route entry is last changed. Each time a route entry is modified, the routing time is set to 0.

RIPng packet format

Basic format

A RIPng packet consists of a header and multiple route table entries (RTEs). The maximum number of RTEs in a packet depends on the IPv6 MTU of the sending interface.

Figure 1 RIPng basic packet format

Packet header description:

· Command: Type of message. 0x01 indicates Request, 0x02 indicates Response.

· Version: Version of RIPng. It can only be 0x01 now.

· RTE: Route table entry, 20 bytes for each entry.

RTE format

The following are types of RTEs in RIPng:

· Next hop RTE—Defines the IPv6 address of a next hop

· IPv6 prefix RTE—Describes the destination IPv6 address, route tag, prefix length and metric in the RIPng routing table.

Figure 2 Next hop RTE format

IPv6 next hop address is the IPv6 address of the next hop.

Figure 3 IPv6 prefix RTE format

· IPv6 prefix—Destination IPv6 address prefix.

· Route tag—Route tag.

· Prefix len—Length of the IPv6 address prefix.

· Metric—Cost of a route.

RIPng packet processing procedure

Request packet

When a RIPng router first starts or needs to update entries in its routing table, usually a multicast request packet is sent to ask for needed routes from neighbors.

The receiving RIPng router processes RTEs in the request. If only one RTE exists with the IPv6 prefix and prefix length both being 0, and with a metric value of 16, the RIPng router will respond with the entire routing table information in response messages. If multiple RTEs exist in the request message, the RIPng router will examine each RTE, update its metric, and send the requested routing information to the requesting router in the response packet.

Response packet

The response packet containing the local routing table information is generated as:

· A response to a request

· An update periodically

· A trigged update caused by route change

After receiving a response, a router checks the validity of the response before adding the route to its routing table, such as whether the source IPv6 address is the link-local address and whether the port number is correct. The response packet that failed the check will be discarded.

Protocols and standards

· RFC 2080, RIPng for IPv6

· RFC 2081, RIPng Protocol Applicability Statement

RIPng configuration task list

Complete the following tasks to configure RIPng:

Task		Remarks
Configuring RIPng basic functions		Required
Configuring RIPng route control	Configuring an additional routing metric	Optional
	Configuring RIPng route summarization	Optional
	Advertising a default route	Optional
	Configuring a RIPng route filtering policy	Optional
	Configuring a priority for RIPng	Optional
	Configuring RIPng route redistribution	Optional
Tuning and optimizing the RIPng network	Configuring RIPng timers	Optional
	Configuring split horizon and poison reverse	Optional
	Configuring zero field check on RIPng packets	Optional
	Configuring the maximum number of equal cost routes for load balancing	Optional

Configuring RIPng basic functions

This section presents the information to configure the basic RIPng features.

You need to enable RIPng first before configuring other tasks, but it is not necessary for RIPng related interface configurations, such as assigning an IPv6 address.

Configuration prerequisites

Before the configuration, complete the following tasks first:

· Enable IPv6 packet forwarding.

· Configure an IP address for each interface, and make sure all nodes are reachable to one another.

Configuration procedure

Follow these steps to configure the basic RIPng functions:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Create a RIPng process and enter RIPng view	ripng [ process-id ]	Required Not created by default
Return to system view	quit	—
Enter interface view	interface interface-type interface-number	––
Enable RIPng on the interface	ripng process-id enable	Required Disabled by default

NOTE:

If RIPng is not enabled on an interface, the interface will not send or receive any RIPng route.

Configuring RIPng route control

This section covers the following topics:

· Configuring RIPng route summarization

· Advertising a default route

· Configuring a RIPng route filtering policy

· Configuring a priority for RIPng

· Configuring RIPng route redistribution

Before configuring RIPng, complete the following tasks:

· Configure an IPv6 address on each interface, and make sure all nodes are reachable to one another.

· Configure RIPng basic functions

· Define an IPv6 ACL before using it for route filtering. See the ACL and QoS Configuration Guide for related information.

Configuring an additional routing metric

An additional routing metric 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. 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, so the route’s metric is changed.

Follow these steps to configure an inbound/outbound additional routing metric:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter interface view	interface interface-type interface-number	––
Specify an inbound routing additional metric	ripng metricin value	Optional 0 by default
Specify an outbound routing additional metric	ripng metricout value	Optional 1 by default

Configuring RIPng route summarization

Follow these steps to configure RIPng route summarization:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter interface view	interface interface-type interface-number	––
Advertise a summary IPv6 prefix	ripng summary-address ipv6-address prefix-length	Required

Advertising a default route

Follow these steps to advertise a default route:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter interface view	interface interface-type interface-number	––
Advertise a default route	ripng default-route { only \| originate } [ cost cost ]	Required Not advertised by default

NOTE:

With this feature enabled, a default route is advertised through the specified interface regardless of whether the default route is available in the local IPv6 routing table.

Configuring a RIPng route filtering policy

You can reference a configured IPv6 ACL or prefix list to filter received/advertised routing information. You can also specify a routing protocol to filter outbound routes redistributed from the protocol.

Follow these steps to configure a RIPng route filtering policy:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter RIPng view	ripng [ process-id ]	––
Configure a filter policy to filter incoming routes	filter-policy { acl6-number \| ipv6-prefix ipv6-prefix-name } import	Required By default, RIPng does not filter incoming routing information.
Configure a filter policy to filter outgoing routes	filter-policy { acl6-number \| ipv6-prefix ipv6-prefix-name } export [ protocol [ process-id ] ]	Required By default, RIPng does not filter outgoing routing information.

Configuring a priority for RIPng

Any routing protocol has its own protocol priority used for optimal route selection. You can set a priority for RIPng manually. The smaller the value is, the higher the priority is.

Follow these steps to configure a RIPng priority:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIPng view	ripng [ process-id ]	—
Configure a RIPng priority	preference preference	Optional By default, the RIPng priority is 100.

Configuring RIPng route redistribution

Follow these steps to configure RIPng route redistribution:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter RIPng view	ripng [ process-id ]	––
Configure a default routing metric for redistributed routes	default cost cost	Optional The default metric of redistributed routes is 0.
Redistribute routes from another routing protocol	import-route protocol [ process-id ] [ cost cost ] *	Required No route redistribution is configured by default.

Tuning and optimizing the RIPng network

This section describes how to tune and optimize the performance of the RIPng network as well as applications under special network environments. Before tuning and optimizing the RIPng network, complete the following tasks:

· Configure a network layer address for each interface

· Configure the basic RIPng functions

This section covers the following topics:

· Configuring RIPng timers

· Configuring split horizon and poison reverse

· Configuring zero field check on RIPng packets

· Configuring the maximum number of equal cost routes for load balancing

Configuring RIPng timers

You can adjust RIPng timers to optimize the performance of the RIPng network.

Follow these steps to configure RIPng timers:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter RIPng view	ripng [ process-id ]	—
Configure RIPng timers	timers { garbage-collect garbage-collect-value \| suppress suppress-value \| timeout timeout-value \| update update-value } *	Optional. The RIPng timers have the following defaults: · 30 seconds for the update timer · 180 seconds for the timeout timer · 120 seconds for the suppress timer · 120 seconds for the garbage-collect timer

NOTE:

When adjusting RIPng timers, consider the network performance and perform unified configurations on routers running RIPng to avoid unnecessary network traffic increase or route oscillation.

Configuring split horizon and poison reverse

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

Enabling split horizon

Split horizon disables RIPng from sending routes through the interface where the routes were learned to prevent routing loops between adjacent routers. Do not disable it unless you make sure that it is necessary.

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	ripng split-horizon	Optional Enabled by default

Enabling poison reverse

Poison reverse allows RIPng 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 configure poison reverse:

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

Configuring zero field check on RIPng packets

Some fields in the RIPng packet must be zero, which are called “zero fields”. With zero field check on RIPng packets enabled, if such a field contains a non-zero value, the entire RIPng packet will be discarded. If you are sure that all packets are reliable, disable the zero field check to reduce the CPU processing time.

Follow these steps to configure RIPng zero field check:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter RIPng view	ripng [ process-id ]	––
Enable the zero field check	checkzero	Optional Enabled by default

Configuring the maximum number of equal cost routes for load balancing

Follow these steps to configure the maximum number of equal cost RIPng routes for load balancing:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter RIPng view	ripng [ process-id ]	––
Configure the maximum number of equal cost RIPng routes for load balancing	maximum load-balancing number	Optional 6 by default

Displaying and maintaining RIPng

To do…	Use the command…	Remarks
Display configuration information of a RIPng process	display ripng [ process-id ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
Display routes in the RIPng database	display ripng process-id database [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
Display the routing information of a specified RIPng process	display ripng process-id route [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
Display RIPng interface information	display ripng process-id interface [ interface-type interface-number ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
Reset a RIPng process	reset ripng process-id process	Available in user view
Clear statistics of a RIPng process	reset ripng process-id statistics	Available in user view

RIPng configuration examples

Configure RIPng basic functions

Network requirements

As shown in Figure 4, all switches run RIPng. Configure Switch B to filter the route (3::/64) learned from Switch C, which means the route will not be added to the routing table of Switch B, and Switch B will not forward it to Switch A.

Figure 4 Network diagram for RIPng configuration

Configuration procedure

1. Configure the IPv6 address for each interface (omitted)

2. Configure basic RIPng functions

# Configure Switch A.

<SwitchA> system-view

[SwitchA] ripng 1

[SwitchA-ripng-1] quit

[SwitchA] interface vlan-interface 100

[SwitchA-Vlan-interface100] ripng 1 enable

[SwitchA-Vlan-interface100] quit

[SwitchA] interface vlan-interface 400

[SwitchA-Vlan-interface400] ripng 1 enable

[SwitchA-Vlan-interface400] quit

# Configure Switch B.

<SwitchB> system-view

[SwitchB] ripng 1

[SwitchB-ripng-1] quit

[SwitchB] interface vlan-interface 200

[SwitchB-Vlan-interface200] ripng 1 enable

[SwitchB-Vlan-interface200] quit

[SwitchB] interface vlan-interface 100

[SwitchB-Vlan-interface100] ripng 1 enable

[SwitchB-Vlan-interface100] quit

# Configure Switch C.

<SwitchC> system-view

[SwitchC] ripng 1

[SwitchC-ripng-1] quit

[SwitchC] interface vlan-interface 200

[SwitchC-Vlan-interface200] ripng 1 enable

[SwitchC-Vlan-interface200] quit

[SwitchC] interface vlan-interface 500

[SwitchC-Vlan-interface500] ripng 1 enable

[SwitchC-Vlan-interface500] quit

[SwitchC] interface vlan-interface 600

[SwitchC-Vlan-interface600] ripng 1 enable

[SwitchC-Vlan-interface600] quit

# Display the routing table of Switch B.

[SwitchB] display ripng 1 route

Route Flags: A - Aging, S - Suppressed, G - Garbage-collect

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

Peer FE80::20F:E2FF:FE23:82F5 on Vlan-interface100

Dest 1::/64,

via FE80::20F:E2FF:FE23:82F5, cost 1, tag 0, A, 6 Sec

Dest 2::/64,

via FE80::20F:E2FF:FE23:82F5, cost 1, tag 0, A, 6 Sec

Peer FE80::20F:E2FF:FE00:100 on Vlan-interface200

Dest 3::/64,

via FE80::20F:E2FF:FE00:100, cost 1, tag 0, A, 11 Sec

Dest 4::/64,

via FE80::20F:E2FF:FE00:100, cost 1, tag 0, A, 11 Sec

Dest 5::/64,

via FE80::20F:E2FF:FE00:100, cost 1, tag 0, A, 11 Sec

# Display the routing table of Switch A.

[SwitchA] display ripng 1 route

Route Flags: A - Aging, S - Suppressed, G - Garbage-collect

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

Peer FE80::200:2FF:FE64:8904 on Vlan-interface100

Dest 1::/64,

via FE80::200:2FF:FE64:8904, cost 1, tag 0, A, 31 Sec

Dest 4::/64,

via FE80::200:2FF:FE64:8904, cost 2, tag 0, A, 31 Sec

Dest 5::/64,

via FE80::200:2FF:FE64:8904, cost 2, tag 0, A, 31 Sec

Dest 3::/64,

via FE80::200:2FF:FE64:8904, cost 1, tag 0, A, 31 Sec

3. Configure Switch B to filter incoming and outgoing routes.

[SwitchB] acl ipv6 number 2000

[SwitchB-acl6-basic-2000] rule deny source 3::/64

[SwitchB-acl6-basic-2000] rule permit

[SwitchB-acl6-basic-2000] quit

[SwitchB] ripng 1

[SwitchB-ripng-1] filter-policy 2000 import

[SwitchB-ripng-1] filter-policy 2000 export

# Display routing tables of Switch B and Switch A.

[SwitchB] display ripng 1 route

Route Flags: A - Aging, S - Suppressed, G - Garbage-collect

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

Peer FE80::20F:E2FF:FE23:82F5 on Vlan-interface100

Dest 1::/64,

via FE80::20F:E2FF:FE23:82F5, cost 1, tag 0, A, 2 Sec

Dest 2::/64,

via FE80::20F:E2FF:FE23:82F5, cost 1, tag 0, A, 2 Sec

Peer FE80::20F:E2FF:FE00:100 on Vlan-interface200

Dest 4::/64,

via FE80::20F:E2FF:FE00:100, cost 1, tag 0, A, 5 Sec

Dest 5::/64,

via FE80::20F:E2FF:FE00:100, cost 1, tag 0, A, 5 Sec

[SwitchA] display ripng 1 route

Route Flags: A - Aging, S - Suppressed, G - Garbage-collect

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

Peer FE80::20F:E2FF:FE00:1235 on Vlan-interface100

Dest 1::/64,

via FE80::20F:E2FF:FE00:1235, cost 1, tag 0, A, 2 Sec

Dest 4::/64,

via FE80::20F:E2FF:FE00:1235, cost 2, tag 0, A, 2 Sec

Dest 5::/64,

via FE80::20F:E2FF:FE00:1235, cost 2, tag 0, A, 2 Sec

Configuring RIPng route redistribution

Network requirements

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

· Configure route redistribution on Switch B, letting the two RIPng processes redistribute routes from each other. Set the default cost of redistributed routes from RIPng 200 to 3.

Figure 5 Network diagram for RIPng route redistribution configuration

Configuration procedure

1. Configure IPv6 addresses for the interfaces (omitted)

2. Configure RIPng basic functions

# Enable RIPng 100 on Switch A.

<SwitchA> system-view

[SwitchA] ripng 100

[SwitchA-ripng-100] quit

[SwitchA] interface vlan-interface 100

[SwitchA-Vlan-interface100] ripng 100 enable

[SwitchA-Vlan-interface100] quit

[SwitchA] interface vlan-interface 200

[SwitchA-Vlan-interface200] ripng 100 enable

[SwitchA-Vlan-interface200] quit

# Enable RIP 100 and RIP 200 on Switch B.

<SwitchB> system-view

[SwitchB] ripng 100

[SwitchB-ripng-100] quit

[SwitchB] interface vlan-interface 100

[SwitchB-Vlan-interface100] ripng 100 enable

[SwitchB-Vlan-interface100] quit

[SwitchB] ripng 200

[SwitchB-ripng-200] quit

[SwitchB] interface vlan-interface 300

[SwitchB-Vlan-interface300] ripng 200 enable

[SwitchB-Vlan-interface300] quit

# Enable RIPng 200 on Switch C.

<SwitchC> system-view

[SwitchC] ripng 200

[SwitchC] interface vlan-interface 300

[SwitchC-Vlan-interface300] ripng 200 enable

[SwitchC-Vlan-interface300] quit

[SwitchC] interface vlan-interface 400

[SwitchC-Vlan-interface400] ripng 200 enable

[SwitchC-Vlan-interface400] quit

# Display the routing table of Switch A.

[SwitchA] display ipv6 routing-table

Routing Table :

Destinations : 6 Routes : 6

Destination: ::1/128 Protocol : Direct

NextHop : ::1 Preference: 0

Interface : InLoop0 Cost : 0

Destination: 1::/64 Protocol : Direct

NextHop : 1::1 Preference: 0

Interface : Vlan100 Cost : 0

Destination: 1::1/128 Protocol : Direct

NextHop : ::1 Preference: 0

Interface : InLoop0 Cost : 0

Destination: 2::/64 Protocol : Direct

NextHop : 2::1 Preference: 0

Interface : Vlan200 Cost : 0

Destination: 2::1/128 Protocol : Direct

NextHop : ::1 Preference: 0

Interface : InLoop0 Cost : 0

Destination: FE80::/10 Protocol : Direct

NextHop : :: Preference: 0

Interface : NULL0 Cost : 0

3. Configure RIPng route redistribution

# Configure route redistribution between the two RIPng processes on Switch B.

[SwitchB] ripng 100

[SwitchB-ripng-100] default cost 3

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

[SwitchB-ripng-100] quit

[SwitchB] ripng 200

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

[SwitchB-ripng-200] quit

# Display the routing table of Switch A.

[SwitchA] display ipv6 routing-table

Routing Table :

Destinations : 7 Routes : 7

Destination: ::1/128 Protocol : Direct

NextHop : ::1 Preference: 0

Interface : InLoop0 Cost : 0

Destination: 1::/64 Protocol : Direct

NextHop : 1::1 Preference: 0

Interface : Vlan100 Cost : 0

Destination: 1::1/128 Protocol : Direct

NextHop : ::1 Preference: 0

Interface : InLoop0 Cost : 0

Destination: 2::/64 Protocol : Direct

NextHop : 2::1 Preference: 0

Interface : Vlan200 Cost : 0

Destination: 2::1/128 Protocol : Direct

NextHop : ::1 Preference: 0

Interface : InLoop0 Cost : 0

Destination: 4::/64 Protocol : RIPng

NextHop : FE80::200:BFF:FE01:1C02 Preference: 100

Interface : Vlan100 Cost : 4

Destination: FE80::/10 Protocol : Direct

NextHop : :: Preference: 0

Interface : NULL0 Cost : 0d

03-Layer 3 Configuration Guide

Introduction to RIPng

RIPng working mechanism

RIPng packet format

Basic format

RTE format

Request packet

Response packet

RIPng configuration task list

Configuring RIPng route control

Configuring an additional routing metric

Configuring RIPng route summarization

Advertising a default route

Configuring a RIPng route filtering policy

Configuring a priority for RIPng

Configuring RIPng route redistribution

Tuning and optimizing the RIPng network

Configuring split horizon and poison reverse

Enabling split horizon

Enabling poison reverse

Configuring zero field check on RIPng packets

Configuring the maximum number of equal cost routes for load balancing

RIPng configuration examples

Network requirements

Configuration procedure

Network requirements

Configuration procedure

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