RIPng uses User Datagram Protocol (UDP) data packets to exchange routing information in small internetworks.

RIPng supports IPv6 and uses the following two message types:

• Request—Sent to the multicast address FF02::9 to request route updates from other RIPng-enabled routers.

• Response—Sent every 30 seconds by default (see the Verifying the RIPng Configuration section). The router also sends response messages after it receives a request message. The response message contains the entire RIPng route table. RIPng sends multiple response packets for a request if the RIPng routing table cannot fit in one response packet.

RIPng uses a hop count for the routing metric. The hop count is the number of routers that a packet can traverse before reaching its destination. A directly connected network has a metric of 1. An unreachable network has a metric of 16. This small range of metrics makes RIPng an unsuitable routing protocol for large networks.

You can use split horizon to ensure that RIPng never advertises a route out of the interface where it was learned.

Split horizon is a method that controls the sending of RIPng update and query packets. When you enable split horizon on an interface, Cisco NX-OS does not send update packets for destinations that were learned from this interface. Controlling update packets in this manner reduces the possibility of routing loops.

You can use split horizon with poison reverse to configure an interface to advertise routes learned by RIPng as unreachable over the interface that learned the routes.

The following figure shows a sample RIPng network with split horizon and poison reverse enabled.

Router C learns about route X and advertises that route to Router B. Router B in turn advertises route X to Router A but sends a route X unreachable update back to Router C.

By default, split horizon is enabled on all interfaces.

You can configure a route policy on an RIPng-enabled interface to filter the RIPng updates. Cisco NX-OS updates the route table with only those routes that the route policy allows.

You can use load balancing to allow a router to distribute traffic over all the router network ports that are the same distance from the destination address. Load balancing increases the usage of network segments and increases effective network bandwidth.

Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in the RIPng route table and the unicast RIB. You can configure RIPng to load balance traffic across some or all of those paths.

Cisco NX-OS supports default-information origination and generation for RIPng IPv6.

To generate a default route into the Routing Information Protocol (RIP), use the default-information originate command in router address-family configuration mode. To disable this feature, use the no form of this command.

default-information originate [always] [route-map map-name]

no default-information originate

Note

Use the always keyword to generate the default route if the route is not present in the RIP routing information base, that is the RIP internal RIB. Use the route-map keyword along with the map-name variable to generate the default route only if the route is permitted by the route map. The map name is any alphanumerical string up to 63 characters. Use the originate to send the default route along with regular updates.

The following example shows how to originate a default route to all routes that pass the condition route map.

switch(config)# router rip Enterprise

switch(config-router)# address-family ipv6 unicast

switch(config-router-af)# default-information originate route-map Condition

Cisco NX-OS supports stateless restarts for RIPng. After a reboot or supervisor switchover, Cisco NX-OS applies the running configuration, and RIPng immediately sends request packets to repopulate its routing table.

Cisco NX-OS supports multiple instances of the RIPng protocol that run on the same system. RIPng supports virtual routing and forwarding (VRF) instances.

RIPng has the following prerequisites:

• You must enable RIPng (see the Enabling RIPng section).

RIPng has the following configuration guidelines and limitations:

• Beginning with Cisco NX-OS Release 10.2(3)F, RIPng feature is introduced to support IPv6 on Cisco Nexus 9300 and 9500 series platform switches.

• Names in the prefix-list are case-insensitive. We recommend using unique names. Do not use the same name by modifying upper-case and lower-case characters. For example, CTCPrimaryNetworks and CtcPrimaryNetworks are not two different entries.

• Cisco NX-OS does not support RIPv1. If Cisco NX-OS receives an RIPv1 packet, it logs a message and drops the packet.

• Cisco NX-OS does not establish adjacencies with RIPv1 routers.

The following example shows how to create the Enterprise RIPng instance in a VRF and add Ethernet interface 1/2 to this RIPng instance.

router rip Enterprise
address-family ipv6 unicast
distance 33
maximum-paths 8
default-information originate always
timers basic 31 181 181 121

interface ethernet 1/2
ipv6 router rip Enterprise

See Configuring Route Policy Manager for more information on route maps.