- Index
- Preface
- Overview
- Using the Command-Line Interface
- Assigning the Switch IP Address and Default Gateway
- Configuring Cisco IOS Configuration Engine
- Administering the Switch
- Configuring Web-Based Authentication
- Clustering Switches
- Managing Switch Stacks
- Configuring SDM Templates
- Configuring Switch-Based Authentication
- Configuring IEEE 802.1x Port-Based Authentication
- Configuring Interface Characteristics
- Configuring VLANs
- Configuring VTP
- Configuring Voice VLAN
- Configuring STP
- Configuring MSTP
- Configuring Optional Spanning-Tree Features
- Configuring Flex Links and the MAC Address-Table Move Update Feature
- Configuring DHCP Features and IP Source Guard
- Configuring Dynamic ARP Inspection
- Configuring IGMP Snooping and MVR
- Configuring Port-Based Traffic Control
- Configuring UDLD
- Configuring CDP
- Configuring LLDP, LLDP-MED, and Wired Location Service
- Configuring SPAN and RSPAN
- Configuring RMON
- Configuring System Message Logging
- Configuring SNMP
- Configuring Cisco IOS IP SLAs Operations
- Configuring Network Security with ACLs
- Configuring QoS
- Configuring Static IP Routing
- Configuring IPv6 Host
- Configuring IPv6 MLD Snooping
- Configuring EtherChannels and Link-State Tracking
- Troubleshooting
- Configuring Online Diagnostics
- Working with the Cisco IOS File System, Configuration Files, and Software Images
- Unsupported Commands in Cisco IOS Release 12.2(58)SE
- Recommendations for Upgrading a Catalyst 2950 Switch to a Catalyst 2960 Switch
Configuring IPv6 Host Functions
This chapter describes how to configure IPv6 host functions on the Catalyst 2960 and 2960-S switches.
For information about configuring IPv6 Multicast Listener Discovery (MLD) snooping, see Chapter1, “Configuring IPv6 MLD Snooping”
To enable dual stack environments (supporting both IPv4 and IPv6) on a Catalyst 2960 switch, you must configure the switch to use the a dual IPv4 and IPv6 switch database management (SDM) template. See the “Dual IPv4 and IPv6 Protocol Stacks” section. This template is not supported on Catalyst 2960-S switches.

Note For complete syntax and usage information for the commands used in this chapter, see the Cisco IOS documentation referenced in the procedures.
Understanding IPv6
IPv4 users can move to IPv6 and receive services such as end-to-end security, quality of service (QoS), and globally unique addresses. The IPv6 address space reduces the need for private addresses and Network Address Translation (NAT) processing by border routers at network edges.
For information about how Cisco Systems implements IPv6, go to:
http://www.cisco.com/en/US/products/ps6553/products_ios_technology_home.html
For information about IPv6 and other features in this chapter:
- See the Cisco IOS IPv6 Configuration Library :
http://www.cisco.com/en/US/docs/ios/12_2t/ipv6/ipv6_vgf.html - Use the Search field to locate the Cisco IOS software documentation. For example, if you want information about static routes, you can enter Implementing Static Routes for IPv6 in the search field to get this document about static routes:
http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-stat_routes_ps6441_TSD_Products_Configuration_Guide_Chapter.html
These sections describe IPv6 implementation on the switch.
IPv6 Addresses
The switch supports only IPv6 unicast addresses. It does not support site-local unicast addresses, anycast addresses, or multicast addresses.
The IPv6 128-bit addresses are represented as a series of eight 16-bit hexadecimal fields separated by colons in the format: n:n:n:n:n:n:n:n. This is an example of an IPv6 address:
2031:0000:130F:0000:0000:09C0:080F:130B
For easier implementation, leading zeros in each field are optional. This is the same address without leading zeros:
You can also use two colons (::) to represent successive hexadecimal fields of zeros, but you can use this short version only once in each address:
For more information about IPv6 address formats, address types, and the IPv6 packet header, see the “Implementing IPv6 Addressing and Basic Connectivity” chapter of Cisco IOS IPv6 Configuration Library on Cisco.com.
In the “Implementing Addressing and Basic Connectivity” chapter, these sections apply to the Catalyst 2960 switch:
Supported IPv6 Host Features
These sections describe the IPv6 protocol features supported by the switch:
- 128-Bit Wide Unicast Addresses
- DNS for IPv6
- ICMPv6
- Neighbor Discovery
- IPv6 Stateless Autoconfiguration and Duplicate Address Detection
- IPv6 Applications
- Dual IPv4 and IPv6 Protocol Stacks
- SNMP and Syslog Over IPv6
- HTTP(S) Over IPv6
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.
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.
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.
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 for host routes or for summarized routes with mask lengths greater than 64 bits.
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.
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:
- Ping, traceroute, and Telnet
- 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
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
On a Catalyst 2960 switch, you must use the dual IPv4 and IPv6 template to allocate ternary content addressable memory (TCAM) usage to both IPv4 and IPv6 protocols.
Dual IPv4 and IPv6 Support on an Interface shows a router forwarding both IPv4 and IPv6 traffic through the same interface, based on the IP packet and destination addresses.
Figure 1-1 Dual IPv4 and IPv6 Support on an Interface

Use the dual IPv4 and IPv6 switch database management (SDM) template on a Catalyst 2960 switch to enable dual stack environments (supporting both IPv4 and IPv6). For more information about the dual IPv4 and IPv6 SDM template, see Chapter1, “Configuring SDM Templates”
The dual IPv4 and IPv6 templates on Catalyst 2960 switches allow the switch to be used in dual stack environments.
- If you try to configure IPv6 without first selecting a dual IPv4 and IPv6 template, a warning message appears.
- In IPv4-only environments, the switch applies IPv4 QoS and ACLs in hardware. IPv6 packets are not supported.
- In dual IPv4 and IPv6 environments, the switch applies IPv4 QoS and ACLs in hardware.
- IPv6 QoS and ACLs are not supported.
- If you do not plan to use IPv6, do not use the dual stack template because this template results in less TCAM capacity for each resource.
For more information about IPv4 and IPv6 protocol stacks, see the “Implementing IPv6 Addressing and Basic Connectivity” chapter of Cisco IOS IPv6 Configuration Library on Cisco.com.
SNMP and Syslog Over IPv6
To support both IPv4 and IPv6, IPv6 network management requires both IPv6 and IPv4 transports. Syslog over IPv6 supports address data types for these transports.
SNMP and syslog over IPv6 provide these features:
- Support for both IPv4 and IPv6
- IPv6 transport for SNMP and to modify the SNMP agent to support traps for an IPv6 host
- SNMP- and syslog-related MIBs to support IPv6 addressing
- Configuration of IPv6 hosts as trap receivers
For support over IPv6, SNMP modifies the existing IP transport mapping to simultaneously support IPv4 and IPv6. These SNMP actions support IPv6 transport management:
- Opens User Datagram Protocol (UDP) SNMP socket with default settings
- Provides a new transport mechanism called SR_IPV6_TRANSPORT
- Sends SNMP notifications over IPv6 transport
- Supports SNMP-named access lists for IPv6 transport
- Supports SNMP proxy forwarding using IPv6 transport
- Verifies SNMP Manager feature works with IPv6 transport
For information on SNMP over IPv6, including configuration procedures, see the “Managing Cisco IOS Applications over IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
For information about syslog over IPv6, including configuration procedures, see the “Implementing IPv6 Addressing and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
HTTP(S) Over IPv6
The HTTP client sends requests to both IPv4 and IPv6 HTTP servers, which respond to requests from both IPv4 and IPv6 HTTP clients. URLs with literal IPv6 addresses must be specified in hexadecimal using 16-bit values between colons.
The accept socket call chooses an IPv4 or IPv6 address family. The accept socket is either an IPv4 or IPv6 socket. The listening socket continues to listen for both IPv4 and IPv6 signals that indicate a connection. The IPv6 listening socket is bound to an IPv6 wildcard address.
The underlying TCP/IP stack supports a dual-stack environment. HTTP relies on the TCP/IP stack and the sockets for processing network-layer interactions.
Basic network connectivity (ping) must exist between the client and the server hosts before HTTP connections can be made.
For more information, see the “Managing Cisco IOS Applications over IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
IPv6 and Switch Stacks
The switch supports IPv6 forwarding across the stack and IPv6 host functionality on the stack master. The stack master runs IPv6 host functionality and IPv6 applications.
While the new stack master is being elected and is resetting, the switch stack does not forward IPv6 packets. The stack MAC address changes, which also changes the IPv6 address. When you specify the stack IPv6 address with an extended unique identifier (EUI) by using the ipv6 address ipv6-prefix/prefix length eui-64 interface configuration command, the address is based on the interface MAC address. See the “Configuring IPv6 Addressing and Enabling IPv6 Host” section.
If you configure the persistent MAC address feature on the stack and the stack master changes, the stack MAC address does not change for approximately 4 minutes. For more information, see the “Enabling Persistent MAC Address” section in Chapter1, “Managing Switch Stacks”
Configuring IPv6
These sections contain this IPv6 forwarding configuration information:
- Default IPv6 Configuration
- Configuring IPv6 Addressing and Enabling IPv6 Host
- Configuring IPv6 ICMP Rate Limiting
- Configuring Static Routes for IPv6
Default IPv6 Configuration
Table 1-1 shows the default IPv6 configuration.
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Configuring IPv6 Addressing and Enabling IPv6 Host
This section describes how to assign IPv6 addresses to individual Layer 3 interfaces and to globally forward IPv6 traffic on the switch.
Before configuring IPv6 on the switch, consider these guidelines:
- Be sure to select a dual IPv4 and IPv6 SDM template.
- In the ipv6 address interface configuration command, you must enter the ipv6-address and ipv6-prefix variables with the address specified in hexadecimal using 16-bit values between colons. The prefix-length variable (preceded by a slash [/]) is a decimal value that shows how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address).
To forward IPv6 traffic on an interface, you must configure a global IPv6 address on that interface. Configuring an IPv6 address on an interface automatically configures a link-local address and activates IPv6 for the interface. The configured interface automatically joins these required multicast groups for that link:
- solicited-node multicast group FF02:0:0:0:0:1:ff00::/104 for each unicast address assigned to the interface (this address is used in the neighbor discovery process.)
- all-nodes link-local multicast group FF02::1
- all-routers link-local multicast group FF02::2
For more information about configuring IPv6, see the “Implementing Addressing and Basic Connectivity for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
Beginning in privileged EXEC mode, follow these steps to assign an IPv6 address to a Layer 3 interface and enable IPv6forwarding:
To remove an IPv6 address from an interface, use the no ipv6 address ipv6-prefix/prefix length eui-64 or no ipv6 address ipv6-address link-local interface configuration command. To remove all manually configured IPv6 addresses from an interface, use the no ipv6 address interface configuration command without arguments. To disable IPv6 processing on an interface that has not been explicitly configured with an IPv6 address, use the no ipv6 enable interface configuration command. To globally disable IPv6 routing, use the no ipv6 unicast-routing global configuration command.
This example shows how to enable IPv6 with both a link-local address and a global address based on the IPv6 prefix 2001:0DB8:c18:1::/64. The EUI-64 interface ID is used in the low-order 64 bits of both addresses. Output from the show ipv6 interface EXEC command shows how the interface ID (20B:46FF:FE2F:D940) is appended to the link-local prefix FE80::/64 of the interface.
Configuring IPv6 ICMP Rate Limiting
ICMP rate limiting is enabled by default with a default interval between error messages of 100 milliseconds and a bucket size (maximum number of tokens to be stored in a bucket) of 10.
Beginning in privileged EXEC mode, follow these steps to change the ICMP rate-limiting parameters:
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Configure the interval and bucket size for IPv6 ICMP error messages: |
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To return to the default configuration, use the no ipv6 icmp error-interval global configuration command.
This example shows how to configure an IPv6 ICMP error message interval of 50 milliseconds and a bucket size of 20 tokens.
Configuring Static Routes for IPv6
Beginning in privileged EXEC mode, follow these steps to configure an IPv6 static route:
To remove a configured static route, use the no ipv6 route ipv6-prefix/prefix length { ipv6-address | interface-id [ ipv6-address ]} [ administrative distance ] global configuration command.
This example shows how to configure a floating static route with an administrative distance of 130 to an interface:
For more information about configuring static IPv6 routing, see the “Implementing Static Routes for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
Displaying IPv6
For complete syntax and usage information on these commands, see the Cisco IOS command reference publications.
Table 1-2 shows the privileged EXEC commands for monitoring IPv6 on the switch.
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Table 1-3 shows the privileged EXEC commands for displaying information about IPv4 and IPv6 address types.
This is an example of the output from the show ipv6 interface privileged EXEC command:
This is an example of the output from the show ipv6 protocols privileged EXEC command:
This is an example of the output from the show ipv6 static privileged EXEC command:
This is an example of the output from the show ipv6 neighbor privileged EXEC command:
This is an example of the output from the show ipv6 route privileged EXEC command:
This is an example of the output from the show ipv6 traffic privileged EXEC command.