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There are two basic steps to activate IPv6 on a router. First you must activate IPv6 traffic
forwarding on the router, and then you must configure each interface that requires IPv6.
By default, IPv6 traffic forwarding is disabled on a Cisco router. To activate IPv6 traffic
forwarding between interfaces, you must configure the global command ipv6 unicastrouting.
This command enables the forwarding of unicast IPv6 traffic.
The ipv6 address command can configure a global IPv6 address. The link-local address is
automatically configured when an address is assigned to the interface. You must specify the
entire 128-bit IPv6 address or specify to use the 64-bit prefix by using the eui-64 option.
You can completely specify the IPv6 address or compute the host identifier (rightmost 64
bits) from the EUI-64 identifier of the interface. In the example shown in Figure 7-18,
the IPv6 address of the interface is configured using the EUI-64 format.
Alternatively, you can completely specify the entire IPv6 address to assign an address to a
router interface using the ipv6 address ipv6-address/prefix-length command in interface
configuration mode.
You can perform name resolution from the Cisco IOS Software process in two ways:
■ It is possible to define a static name for IPv6 addresses using the command ipv6 host
name [port] ipv6-address1 [ipv6-address2 . . . ipv6-address4].You can define up to
four IPv6 addresses for one hostname. The port option refers to the Telnet port that
should be used for the associated host.
■ To specify the DNS server used by the router, use the ip name-server address
command. The address can be an IPv4 or IPv6 address. You can specify up to six DNS
servers with this command.
Configuring and Verifying RIPng for IPv6
The following paragraph describes the syntax of some commands that are commonly used
to configure RIPng. The syntax is similar, if not identical, to their IPv4 counterparts. For
NOTE The configuration of the IPv6 address on an interface automatically configures
the link-local address for that interface.
288 Chapter 7: Managing Address Spaces with NAT and IPv6
RIPng, instead of using the network command to identify which interfaces should run
RIPng, you use the command ipv6 rip tag enable in interface configuration mode to enable
RIPng on an interface. The tag parameter that you use for the ipv6 rip enable command
must match the tag parameter in the ipv6 router rip command.
Example: RIPng for IPv6 Configuration
Figure 7-18 shows a network of two routers. Router Y is connected to the default network.
On both Router X and Router Y, “RT0” is a tag that identifies the RIPng process. RIPng is
enabled on the first Ethernet interface of Router Y using the ipv6 rip RT0 enable
command. Router X shows that RIPng is enabled on both Ethernet interfaces using the ipv6
rip RT0 enable command.
Figure 7-18 RIPng Configuration Example
NOTE Enabling RIP on an interface dynamically creates a “router rip” process if
necessary.
LAN1: 2001:db8:1:1::/64
LAN2: 2001:db8:1:2::/64
Ethernet0
Ethernet1
RouterY#
ipv6 unicast-routing
ipv6 router rip RT0
interface Ethernet0
ipv6 address 2001:db8:1:1::/64 eui-64
ipv6 rip RT0 enable
RouterX#
ipv6 unicast-routing
ipv6 router rip RT0
interface Ethernet0
ipv6 address 2001:db8:1:1::/64 eui-64
ipv6 rip RT0 enable
interface Ethernet1
ipv6 address 2001:db8:1:2::/64 eui-64
ipv6 rip RT0 enable
Router X
Router Y
::/0
Chapter Summary 289
Summary of Transitioning to IPv6
The following summarizes the key points that were discussed in this section:
■ IPv6 offers many additional benefits to IPv4, including a larger address space, easier
address aggregation, and integrated security.
■ The IPv6 address is 128 bits long and is made up of a 48-bit global prefix, a 16-bit
subnet ID, and a 64-bit interface identifier.
■ There are several ways to assign IPv6 addresses—statically, stateless
autoconfiguration, and DHCPv6.
■ Cisco supports all the major IPv6 routing protocols—RIPng, OSPFv3, and EIGRP.
■ Transitioning from IPv4 to IPv6 requires dual stacks, tunneling, and possibly NAT-PT.
■ Use the ipv6 unicast-routing command to enable IPv6 and the ipv6 address ipv6-
address/prefix-length command to assign interface addresses and enable an IPv6
routing protocol.
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