IPv6 Routing: RIP for IPv6

IPv6 RIP functions the same and offers the same benefits as RIP in IPv4. RIP enhancements for IPv6, detailed in RFC 2080, include support for IPv6 addresses and prefixes, and the use of the all-RIP-routers multicast group address FF02::9 as the destination address for RIP update messages.

In the Cisco software implementation of IPv6 RIP, each IPv6 RIP process maintains a local routing table, referred to as a Routing Information Database (RIB). The IPv6 RIP RIB contains a set of best-cost IPv6 RIP routes learned from all its neighboring networking devices. If IPv6 RIP learns the same route from two different neighbors, but with different costs, it will store only the lowest cost route in the local RIB. The RIB also stores any expired routes that the RIP process is advertising to its neighbors running RIP. IPv6 RIP will try to insert every non-expired route from its local RIB into the master IPv6 RIB. If the same route has been learned from a different routing protocol with a better administrative distance than IPv6 RIP, the RIP route will not be added to the IPv6 RIB but the RIP route will still exist in the IPv6 RIP RIB.

Cisco nonstop forwarding (NSF) continues forwarding packets while routing protocols converge, therefore avoiding a route flap on switchover. When an RP failover occurs, the Forwarding Information Base (FIB) marks installed paths as stale by setting a new epoch. Subsequently, the routing protocols reconverge and populate the RIB and FIB. Once all NSF routing protocols converge, any stale routes held in the FIB are removed. A failsafe timer is required to delete stale routes, in case of routing protocol failure to repopulate the RIB and FIB.

RIP registers as an IPv6 NSF client. Doing so has the benefit of using RIP routes installed in the Cisco Express Forwarding table until RIP has converged on the standby.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 unicast-routing

4.    interface type number

5.   ipv6 enable

6.    ipv6 rip name enable

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Device> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	ipv6 unicast-routing Example: Device(config)# ipv6 unicast-routing	Enables the forwarding of IPv6 unicast datagrams.
Step 4	interface type number Example: Device(config)# interface Ethernet 0/0	Specifies the interface type and number, and enters interface configuration mode.
Step 5	ipv6 enable Example: Device(config-if)# ipv6 enable	Enables IPv6 processing on an interface that has not been configured with an explicit IPv6 address.
Step 6	ipv6 rip name enable Example: Device(config-if)# ipv6 rip process1 enable	Enables the specified IPv6 RIP routing process on an interface.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 router rip word

4.    maximum-paths number-paths

5.    exit

6.    interface type number

7.    ipv6 rip name default-information {only | originate} [metric metric-value]

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	ipv6 router rip word Example: Router(config)# ipv6 router rip process1	Configures an IPv6 RIP routing process and enters router configuration mode for the IPv6 RIP routing process. Use the wordargument to identify a specific IPv6 RIP routing process.
Step 4	maximum-paths number-paths Example: Router(config-router)# maximum-paths 1	(Optional) Defines the maximum number of equal-cost routes that IPv6 RIP can support. The number-paths argument is an integer from 1 to 64. The default for RIP is four paths.
Step 5	exit Example: Router(config-if)# exit	Exits interface configuration mode and enters global configuration mode.
Step 6	interface type number Example: Router(config)# interface Ethernet 0/0	Specifies the interface type and number, and enters interface configuration mode.
Step 7	ipv6 rip name default-information {only | originate} [metric metric-value] Example: Router(config-if)# ipv6 rip process1 default-information originate	(Optional) Originates the IPv6 default route (::/0) into the specified RIP routing process updates sent out of the specified interface. Note    To avoid routing loops after the IPv6 default route (::/0) is originated out of any interface, the routing process ignores all default routes received on any interface. Specifying the only keyword originates the default route (::/0) but suppresses all other routes in the updates sent on this interface. Specifying the originate keyword originates the default route (::/0) in addition to all other routes in the updates sent on this interface.

SUMMARY STEPS

1.    show ipv6 rip [name][database| next-hops]

2.    show ipv6 route [ipv6-address| ipv6-prefix/prefix-length| protocol | interface-type interface-number]

3.    enable

4.    debug ipv6 rip [interface-type interface-number]

DETAILED STEPS

	Command or Action	Purpose
Step 1	show ipv6 rip [name][database| next-hops] Example: Router> show ipv6 rip process1 database	(Optional) Displays information about current IPv6 RIP processes. In this example, IPv6 RIP process database information is displayed for the specified IPv6 RIP process.
Step 2	show ipv6 route [ipv6-address| ipv6-prefix/prefix-length| protocol | interface-type interface-number] Example: Router> show ipv6 route rip	(Optional) Displays the current contents of the IPv6 routing table. In this example, only IPv6 RIP routes are displayed.
Step 3	enable Example: Router> enable	Enables higher privilege levels, such as privileged EXEC mode. Enter your password if prompted.
Step 4	debug ipv6 rip [interface-type interface-number] Example: Router# debug ipv6 rip	(Optional) Displays debugging messages for IPv6 RIP routing transactions.

In the following example, the IPv6 RIP process named process1 is enabled on the router and on Ethernet interface 0/0. The IPv6 default route (::/0) is advertised in addition to all other routes in router updates sent on Ethernet interface 0/0. Additionally, BGP routes are redistributed into the RIP process named process1 according to a route map where routes that match a prefix list are also tagged. The number of parallel paths is set to one to allow the route tagging, and the IPv6 RIP timers are adjusted. A prefix list named eth0/0-in-flt filters inbound routing updates on Ethernet interface 0/0.

ipv6 router rip process1
 maximum-paths 1
 redistribute bgp 65001 route-map bgp-to-rip
 distribute-list prefix-list eth0/0-in-flt in Ethernet0/0
!
interface Ethernet0/0
 ipv6 address 2001:DB8::/64 eui-64
 ipv6 rip process1 enable
 ipv6 rip process1 default-information originate
!
ipv6 prefix-list bgp-to-rip-flt seq 10 deny 2001:DB8:3::/16 le 128
ipv6 prefix-list bgp-to-rip-flt seq 20 permit 2001:DB8:1::/8 le 128
!
ipv6 prefix-list eth0/0-in-flt seq 10 deny ::/0
ipv6 prefix-list eth0/0-in-flt seq 15 permit ::/0 le 128
!
route-map bgp-to-rip permit 10
 match ipv6 address prefix-list bgp-to-rip-flt
 set tag 4

In the following example, output information about all current IPv6 RIP processes is displayed using the show ipv6 rip command:

Device> show ipv6 rip

RIP process "process1", port 521, multicast-group FF02::9, pid 62
     Administrative distance is 120. Maximum paths is 1
     Updates every 5 seconds, expire after 15
     Holddown lasts 10 seconds, garbage collect after 30
     Split horizon is on; poison reverse is off
     Default routes are generated
     Periodic updates 223, trigger updates 1
  Interfaces:
    Ethernet0/0
  Redistribution:
    Redistributing protocol bgp 65001 route-map bgp-to-rip

In the following example, output information about a specified IPv6 RIP process database is displayed using the show ipv6 rip command with the name argument and the database keyword. In the following output for the IPv6 RIP process named process1, timer information is displayed, and route 2001:DB8::16/64 has a route tag set:

Device> show ipv6 rip process1 database

RIP process "process1", local RIB
 2001:DB8::/64, metric 2
     Ethernet0/0/FE80::A8BB:CCFF:FE00:B00, expires in 13 secs
 2001:DB8::/16, metric 2 tag 4, installed
     Ethernet0/0/FE80::A8BB:CCFF:FE00:B00, expires in 13 secs
 2001:DB8:1::/16, metric 2 tag 4, installed
     Ethernet0/0/FE80::A8BB:CCFF:FE00:B00, expires in 13 secs
 2001:DB8:2::/16, metric 2 tag 4, installed
     Ethernet0/0/FE80::A8BB:CCFF:FE00:B00, expires in 13 secs
 ::/0, metric 2, installed
     Ethernet0/0/FE80::A8BB:CCFF:FE00:B00, expires in 13 secs

In the following example, output information for a specified IPv6 RIP process is displayed using the show ipv6 rip command with the name argument and the next-hops keyword:

Device> show ipv6 rip process1 next-hops

RIP process "process1", Next Hops
  FE80::A8BB:CCFF:FE00:A00/Ethernet0/0 [4 paths]