Filter
Top Products
39-7
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02
Chapter 39 Configuring IPv6 Unicast Routing
Understanding IPv6
• Simple Network Management Protocol (SNMP) over IPv6 transport
• IPv6 Hot Standby Router Protocol (HSRP)
• DHCPv6
• IPv6 packets destined to site-local addresses
• Tunneling protocols, such as IPv4-to-IPv6 or IPv6-to-IPv4
• The switch as a tunnel endpoint supporting IPv4-to-IPv6 or IPv6-to-IPv4 tunneling protocols
• IPv6 unicast reverse-path forwarding
• IPv6 general prefixes
Limitations
Because IPv6 is implemented in hardware in the switch, some limitations occur due to the use of IPv6
compressed addresses in the hardware memory. These hardware limitations result in some loss of
functionality and limits some features.
These are feature limitations.
• Load-balancing using equal cost and unequal cost routes is not supported for IPv6 host routes or for
IPv6 routes with a mask greater than 64.
• The switch cannot correctly forward SNAP-encapsulated IPv6 packets. These packets are corrupted
before being forwarded (bridged or routed) and reach the network as corrupted packets.
Note There is a similar limitation for IPv4 SNAP-encapsulated packets, but the packets are
dropped at the switch and are not forwarded as corrupted packets.
• The switch routes IPv6-to-IPv4 and IPv4-to-IPv6 packets in hardware, but the switch cannot be an
IPv6-to-IPv4 or IPv4-to-IPv6 tunnel endpoint.
• Bridged IPv6 packets with hop-by-hop extension headers are forwarded in software. In IPv4, these
packets are routed in software, but bridged in hardware.
• In addition to the normal SPAN and RSPAN limitations defined in the software configuration guide,
these limitations are specific to IPv6 packets:
–
When you egress RSPAN IPv6-routed packets, the source MAC address in the SPAN output
packet can be corrupted.
–
When you egress RSPAN IPv6-routed packets, the destination MAC address can be corrupted.
Normal traffic is not affected.
• The switch cannot apply QoS classification, or policy-based routing on source-routed IPv6 packets
in hardware.
• The switch cannot generate ICMPv6
Packet Too Big
messages for multicast packets.
IPv6 and Switch Stacks
The switch supports IPv6 forwarding across the stack much the same as with IPv4 unicast routing. The
stack master runs the IPv6 unicast routing protocols and computes the routing tables. Using distributed
CEF (dCEF), the stack master downloads the routing table to the stack member switches. The member
switches receive the tables and install IPv6 routes into hardware for hardware forwarding.