IPv6 Configuration Guide K/KA/KB.15.15

3. Enable IPv6 routing. (This command enables RA transmission on any VLAN where RAs are
not specifically suppressed.)
ipv6 unicast-routing
4. For non-default RA operation, configure RAs per-VLAN, including suppression of RAs on any
VLANs where you do not want the routing switch to transmit RAs. See “IPv6 Router
Advertisements” (page 186).
5. Configure one or more of the following routing features:
• IPv6 static routing. See “IPv6 Static Routing” (page 180).
• DHCPv6-relay. See “DHCPv6-Relay” (page 203).
• OSPFv3. See “OSPFv3 Routing” (page 209).
Configuring a router ID
For more information on configuring routers, see “Configuring global IPv6 routing parameters”
(page 176).
When router ospf3 enable is used to enable OSPFv3 on a routing switch, the following
message appears if an IPv4 network or loopback address is not detected:
Either an IPv4 loopback address or a router ID needs to be configured before
enabling OSPFv3.
Do you want to continue? [y/n]
Typing N (no) keeps OSPFv3 disabled. Typing Y allows OSPFv3 to be enabled without a router
ID. However, without the ID, OSPFv3 traffic is not routed. In this case do one of the following:
• Configure an IPv4 address on a loopback interface or VLAN.
• Manually configure a router ID on the routing switch.
IPv6 networks and subnets
An IPv6 network is a group of hosts and routers that share a common network prefix and exist on
the same VLAN interface. Where multiple unique network prefixes exist on the VLAN, each prefix
corresponds to a different subnet. For example, if a given network has a prefix of
2001:db8:1ad:27b::/64, any global unicast address for an individual device belonging to this
network has:
• The same prefix (2001:db8:1ad:27b::/64).
• A unique value (for the interface ID) in the remaining 64 bits of the global unicast addresses.
In the above case, if device "A" has an interface ID of 218:71ff:fedd:cf00, its complete global
unicast address is:
2001:db8:1ad:27b:218:71ff:fedd:cf00/64
1 2 3
321
Prefix LengthInterface IDPrefix
Traffic between hosts on the same network is switched and employs link-local addresses that include
a reserved prefix (FE80::/64) and a unique interface ID generated from the device MAC address.
See “IPv6 Addressing Configuration” (page 11). Continuing the example from above, device "A"
uses the following link-local address for switching:
However, when a packet must be sent from one network to another, where the source and
destination have different IPv6 network prefixes, the packet must be routed. For example, routing
is required to send traffic between the devices at these two addresses residing in different networks:
2620:0:a03:e102:218:71ff:fedd:cf00/64
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172 IPv6 Routing Basics