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Chapter 37 Configuring IPv6 Unicast Routing
Understanding IPv6
• Neighbor Discovery, page 37-4
• Default Router Preference, page 37-4
• IPv6 Stateless Autoconfiguration and Duplicate Address Detection, page 37-5
• IPv6 Applications, page 37-5
• Dual IPv4 and IPv6 Protocol Stacks, page 37-5
• DHCP for IPv6 Address Assignment, page 37-6
• Static Routes for IPv6, page 37-6
• RIP for IPv6, page 37-6
• OSPF for IPv6, page 37-6 (only on switches running the IP services image)
• EIGRP for IPv6, page 37-7 (only on switches running the IP services image)
• HSRP for IPv6, page 37-7 (only on switches running the IP services image)
• SNMP and Syslog Over IPv6, page 37-7
• HTTP(S) Over IPv6, page 37-8
Support on the switch includes expanded address capability, header format simplification, improved
support of extensions and options, and hardware parsing of the extension header. The switch supports
hop-by-hop extension header packets, which are routed or bridged in software.
The switch provides IPv6 routing capability over native Ethernet Inter-Switch Link (ISL) or 802.1Q
trunk ports for static routes, Routing Information Protocol (RIP) for IPv6, and Open Shortest Path First
(OSPF) Version 3 Protocol. It supports up to 16 equal-cost routes and can simultaneously forward IPv4
and IPv6 frames at line rate.
128-Bit Wide Unicast Addresses
The switch supports aggregatable global unicast addresses and link-local unicast addresses. It does not
support site-local unicast addresses.
• Aggregatable global unicast addresses are IPv6 addresses from the aggregatable global unicast
prefix. The address structure enables strict aggregation of routing prefixes and limits the number of
routing table entries in the global routing table. These addresses are used on links that are aggregated
through organizations and eventually to the Internet service provider.
These addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Current
global unicast address allocation uses the range of addresses that start with binary value 001
(2000::/3). Addresses with a prefix of 2000::/3(001) through E000::/3(111) must have 64-bit
interface identifiers in the extended unique identifier (EUI)-64 format.
• Link local unicast addresses can be automatically configured on any interface by using the link-local
prefix FE80::/10(1111 1110 10) and the interface identifier in the modified EUI format. Link-local
addresses are used in the neighbor discovery protocol (NDP) and the stateless autoconfiguration
process. Nodes on a local link use link-local addresses and do not require globally unique addresses
to communicate. IPv6 routers do not forward packets with link-local source or destination addresses
to other links.
For more information, see the section about IPv6 unicast addresses in the “Implementing IPv6
Addressing and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.