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Chapter 39
Configuring IPv6 Unicast Routing
Neighbor discovery throttling ensures that the switch CPU is not unnecessarily burdened while it is in
the process of obtaining the next hop forwarding information to route an IPv6 packet. The switch drops
any additional IPv6 packets whose next hop is the same neighbor that the switch is actively trying to
resolve. This drop avoids further load on the CPU.
Default Router Preference
The switch supports IPv6 default router preference (DRP), an extension in router advertisement
messages. DRP improves the ability of a host to select an appropriate router, especially when the host is
multihomed and the routers are on different links. The switch does not support the Route Information
Option in RFC 4191.
An IPv6 host maintains a default router list from which it selects a router for traffic to offlink
destinations. The selected router for a destination is then cached in the destination cache. NDP for IPv6
specifies that routers that are reachable or probably reachable are preferred over routers whose
reachability is unknown or suspect. For reachable or probably reachable routers, NDP can either select
the same router every time or cycle through the router list. By using DRP, you can configure an IPv6
host to prefer one router over another, provided both are reachable or probably reachable.
For more information about DRP for IPv6, see the "Implementing IPv6 Addresses and Basic
Connectivity" chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
IPv6 Stateless Autoconfiguration and Duplicate Address Detection
The switch uses stateless autoconfiguration to manage link, subnet, and site addressing changes, such as
management of host and mobile IP addresses. A host autonomously configures its own link-local
address, and booting nodes send router solicitations to request router advertisements for configuring
interfaces.
For more information about autoconfiguration and duplicate address detection, see the "Implementing
IPv6 Addressing and Basic Connectivity" chapter of Cisco IOS IPv6 Configuration Library on
Cisco.com.
IPv6 Applications
The switch has IPv6 support for these applications:
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For more information about managing these applications, see the "Managing Cisco IOS Applications
over IPv6" chapter and the "Implementing IPv6 Addressing and Basic Connectivity" chapter in the
Cisco IOS IPv6 Configuration Library on Cisco.com.
Dual IPv4 and IPv6 Protocol Stacks
You must use the dual IPv4 and IPv6 template to allocate ternary content addressable memory (TCAM)
usage to both IPv4 and IPv6 protocols.
OL-12247-04
Ping, traceroute, Telnet, TFTP, and FTP
Secure Shell (SSH) over an IPv6 transport
HTTP server access over IPv6 transport
DNS resolver for AAAA over IPv4 transport
Cisco Discovery Protocol (CDP) support for IPv6 addresses
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
Understanding IPv6
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