Cisco Catalyst 3750-X User Manual

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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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Chapter 43 Configuring IPv6 Unicast Routing
Understanding IPv6
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 u
nicast addresses in the “Implementing IPv6
Addressing and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
DNS for IPv6
IPv6 supports Domain Name System (DNS) record types in the DNS name-to-address and
address-to-name lookup processes. The DNS AAAA resource record types support IPv6 addresses and
are equivalent to an A address record in IPv4. The switch supports DNS resolution for IPv4 and IPv6.
Path MTU Discovery for IPv6 Unicast
The switch supports advertising the system maximum transmission unit (MTU) to IPv6 nodes and path
MTU discovery. Path MTU discovery allows a host to dynamically discover and adjust to differences in
the MTU size of every link along a given data path. In IPv6, if a link along the path is not large enough
to accommodate the packet size, the source of the packet handles the fragmentation. The switch does not
support path MTU discovery for multicast packets.
ICMPv6
The Internet Control Message Protocol (ICMP) in IPv6 generates error messages, such as ICMP
destination unreachable messages, to report errors during processing and other diagnostic functions. In
IPv6, ICMP packets are also used in the neighbor discovery protocol and path MTU discovery.
Neighbor Discovery
The switch supports NDP for IPv6, a protocol running on top of ICMPv6, and static neighbor entries for
IPv6 stations that do not support NDP. The IPv6 neighbor discovery process uses ICMP messages and
solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network
(local link), to verify the reachability of the neighbor, and to keep track of neighboring routers.
The switch supports ICMPv6 redirect for routes with mask lengths less than 64 bits. ICMP redirect is
not supported f
or host routes or for summarized routes with mask lengths greater than 64 bits.
Neighbor discovery throttling ensures that the switch CPU is no
t 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
de
stinations. 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

Cisco Catalyst 3750-X Specifications

General

Switching Capacity	160 Gbps
Stacking Bandwidth	64 Gbps
Max Stacking Units	9
Layer Support	Layer 2 and Layer 3
Form Factor	Rack-mountable
DRAM	256 MB
Flash Memory	64 MB
Model	Cisco Catalyst 3750-X Series
Ports	24 or 48 10/100/1000 Ethernet ports
Uplink Interfaces	4 SFP or 2 SFP+
Features	StackWise Plus, EnergyWise
Image	IP Base or IP Services
Operating Temperature	0 to 40°C
Operating Humidity	10 to 85% noncondensing