Configuring IPv6 Unicast Routing

Information About Configuring IPv6 Unicast Routing

This chapter describes how to configure IPv6 unicast routing on the switch.


Note
To use all IPv6 features in this chapter, the switch or active switch must be running the Network Advantage license. Switches running the Network Essentials license support IPv6 static routing and RIP for IPv6. Switches running the Network Advantage license support OSPF, EIGRP and BGP for IPv6.

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.

  • Use the Search field on Cisco.com 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 learn about static routes.

Static Routes for IPv6

Static routes are manually configured and define an explicit route between two networking devices. Static routes are useful for smaller networks with only one path to an outside network or to provide security for certain types of traffic in a larger network.

Configuring Static Routing for IPv6 (CLI)

For configuring static routes for IPv6, see the Configuring Static Routing for IPv6 section.

For more information about static routes, see the “Implementing Static Routes for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.

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.

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 Router Advertisement Options for DNS Configuration

Most of the internet services are identified by a Domain Name Server (DNS) name. IPv6 Router Advertisement (RA) provides the following two options to allow IPv6 hosts to perform automatic DNS configuration:

  • Recursive DNS Server (RDNSS)

  • DNS Search List (DNSSL)

RDNSS contains the address of recursive DNS servers that help in DNS name resolution in IPv6 hosts. DNS Search List is a list of DNS suffix domain names used by IPv6 hosts when they perform DNS query searches.

For more information on RA options for DNS configuration, refer IETF RFC 6106.

For configuring DNSSL, see the Configuring DNS Search List Using IPv6 Router Advertisement Options section of the IP Addressing Services Configuration Guide.

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 configuring DRP for IPv6, see the Configuring Default Router Preference section.

For more information about DRP for IPv6, see the Cisco IOS IPv6 Configuration Library on Cisco.com.

Policy-Based Routing for IPv6

Policy-based routing (PBR) gives you a flexible means of routing packets by allowing you to configure a defined policy for traffic flows, which lessens reliance on routes derived from routing protocols. Therefore, PBR gives you more control over routing by extending and complementing the existing mechanisms provided by routing protocols. PBR allows you to set the IPv6 precedence. For a simple policy, you can use any one of these tasks; for a complex policy, you can use all of them. It also allows you to specify a path for certain traffic, such as priority traffic over a high-cost link.

PBR for IPv6 may be applied to both forwarded and originated IPv6 packets. For forwarded packets, PBR for IPv6 will be implemented as an IPv6 input interface feature, supported in the following forwarding paths:

  • Process

  • Cisco Express Forwarding (formerly known as CEF)

  • Distributed Cisco Express Forwarding

Policies can be based on the IPv6 address, port numbers, protocols, or packet size.

PBR allows you to perform the following tasks:

  • Classify traffic based on extended access list criteria. Access lists, then, establish the match criteria.

  • Set IPv6 precedence bits, giving the network the ability to enable differentiated classes of service.

  • Route packets to specific traffic-engineered paths; you might need to route them to allow a specific quality of service (QoS) through the network.

PBR allows you to classify and mark packets at the edge of the network. PBR marks a packet by setting precedence value. The precedence value can be used directly by devices in the network core to apply the appropriate QoS to a packet, which keeps packet classification at your network edge.

For enabling PBR for IPv6, see the Enabling Local PBR for IPv6 section.

For enabling IPv6 PBR for an interface, see the Enabling IPv6 PBR on an Interface section.

Unsupported IPv6 Unicast Routing Features

The switch does not support these IPv6 features:

  • VPN is supported on Cisco Catalyst 9500 Series Switches - High Performance.

  • 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 Web Cache Communication Protocol (WCCP)

IPv6 Feature Limitations

Because IPv6 is implemented in switch hardware, some limitations occure due to the IPv6 compressed addresses in the hardware memory. This hardware limitation result in some loss of functionality and limits some features. For example, the switch cannot apply QoS classification on source-routed IPv6 packets in hardware.

IPv6 and Switch Stacks

The switch supports IPv6 forwarding across the stack and IPv6 host functionality on the active switch. The active switch runs the IPv6 unicast routing protocols and computes the routing tables. They receive the tables and create hardware IPv6 routes for forwarding. The active switch also runs all IPv6 applications.

If a new switch becomes the active switch, it recomputes the IPv6 routing tables and distributes them to the member switches. While the new active switch 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 Routing section.

If you configure the persistent MAC address feature on the stack and the active switch changes, the stack MAC address does not change for approximately 4 minutes.

These are the functions of IPv6 active switch and members:

  • Active switch:

    • runs IPv6 routing protocols

    • generates routing tables

    • distributes routing tables to member switches that use distributed Cisco Express Forwarding for IPv6

    • runs IPv6 host functionality and IPv6 applications

  • Member switch:

    • receives Cisco Express Forwarding for IPv6 routing tables from the active switch

    • programs the routes into hardware


    Note

    IPv6 packets are routed in hardware across the stack if the packet does not have exceptions (IPv6 Options) and the switches in the stack have not run out of hardware resources.

    • flushes the Cisco Express Forwarding for IPv6 tables on active switch re-election

Default IPv6 Configuration

Table 1. Default IPv6 Configuration

Feature

Default Setting

SDM template

Default is core template

IPv6 routing

Disabled globally and on all interfaces

Cisco Express Forwarding for IPv6 or distributed Cisco Express Forwarding for IPv6

Disabled (IPv4 Cisco Express Forwarding and distributed Cisco Express Forwarding are enabled by default)

Note

 

When IPv6 routing is enabled, Cisco Express Forwarding for IPv6 and distributed Cisco Express Forwarding for IPv6 are automatically enabled.

IPv6 addresses

None configured

How to Configure IPv6 Unicast Routing

The following sections shows the various configuration options available for IPv6 Unicast Routing

Configuring IPv6 Addressing and Enabling IPv6 Routing

This section describes how to assign IPv6 addresses to individual Layer 3 interfaces and to globally forward IPv6 traffic on the switch.


Note

IPv6 routing is not enabled by default and needs to be enabled using the ipv6 unicast-routing command.

Before configuring IPv6 on the switch, consider these guidelines:

  • Not all features discussed in this chapter are supported by the switch. See the Unsupported IPv6 Unicast Routing Features.

  • 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

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.

For more information about configuring IPv6 routing, see the “Implementing Addressing and Basic Connectivity for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.

To assign an IPv6 address to a Layer 3 interface and enable IPv6 routing, perform this procedure:

Procedure

  Command or Action Purpose

Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

sdm prefer {core | distribution | nat | sda}

Example:


Device(config)# sdm prefer core

Selects an SDM template:

  • core—Sets the switch to the default template.

  • distribution —Sets the distribution template

  • nat —Maximizes the NAT configuration on the switch.

  • sda —Sets the sda template

Step 4

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Step 5

reload

Example:


Device# reload

Reloads the operating system.

Step 6

configure terminal

Example:


Device# configure terminal

Enters global configuration mode after the switch reloads.

Step 7

interface interface-id

Example:


Device(config)# interface gigabitethernet 1/0/1

Enters interface configuration mode, and specifies the Layer 3 interface to configure. The interface can be a physical interface, a switch virtual interface (SVI), or a Layer 3 EtherChannel.

Step 8

no switchport

Example:


Device(config-if)# no switchport

Removes the interface from Layer 2 configuration mode (if it is a physical interface).

Step 9

Use one of the following:

  • ipv6 address ipv6-prefix/prefix length eui-64
  • ipv6 address ipv6-address/prefix length
  • ipv6 address ipv6-address link-local
  • ipv6 enable
  • ipv6 address WORD
  • ipv6 address autoconfig
  • ipv6 address dhcp

Example:

Device(config-if)# ipv6 address 2001:0DB8:c18:1::/64 eui 64


Device(config-if)# ipv6 address 2001:0DB8:c18:1::/64


Device(config-if)# ipv6 address 2001:0DB8:c18:1:: link-local


Device(config-if)# ipv6 enable

  • Specifies a global IPv6 address with an extended unique identifier (EUI) in the low-order 64 bits of the IPv6 address. Specify only the network prefix; the last 64 bits are automatically computed from the switch MAC address. This enables IPv6 processing on the interface.

  • Manually configures an IPv6 address on the interface.

  • Specifies a link-local address on the interface to be used instead of the link-local address that is automatically configured when IPv6 is enabled on the interface. This command enables IPv6 processing on the interface.

  • Automatically configures an IPv6 link-local address on the interface, and enables the interface for IPv6 processing. The link-local address can only be used to communicate with nodes on the same link.

Step 10

exit

Example:


Device(config-if)# exit

Returns to global configuration mode.

Step 11

ip routing

Example:


Device(config)# ip routing

Enables IP routing on the switch.

Note

 

On the C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches, IP routing is enabled on the device by default.

Step 12

ipv6 unicast-routing

Example:


Device(config)# ipv6 unicast-routing

Enables forwarding of IPv6 unicast data packets.

Step 13

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Step 14

show ipv6 interface interface-id

Example:


Device# show ipv6 interface gigabitethernet 1/0/1

Verifies your entries.

Step 15

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring IPv4 and IPv6 Protocol Stacks

Beginning in privileged EXEC mode, follow these steps to configure a Layer 3 interface to support both IPv4 and IPv6 and to enable IPv6 routing.


Note
To disable IPv6 processing on an interface that has not been configured with an IPv6 address, use the no ipv6 enable command in interface configuration mode.

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip routing

Example:

Device(config)# ip routing

Enables routing on the switch.

Note

 

On the C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches, IP routing is enabled on the device by default.

Step 4

ipv6 unicast-routing

Example:

Device(config)# ipv6 unicast-routing

Enables forwarding of IPv6 data packets on the switch.

Step 5

interface interface-id

Example:

Device(config)# interface gigabitethernet 1/0/1

Enters interface configuration mode, and specifies the Layer 3 interface to configure.

Step 6

no switchport

Example:

Device(config-if)# no switchport

Removes the interface from Layer 2 configuration mode (if it is a physical interface).

Step 7

ip address ip-address mask [secondary]

Example:

Device(config-if)# ip address 10.1.2.3 255.255.255

Specifies a primary or secondary IPv4 address for the interface.

Step 8

Use one of the following:

  • ipv6 address ipv6-prefix/prefix length eui-64
  • ipv6 address ipv6-address/prefix length
  • ipv6 address ipv6-address link-local
  • ipv6 enable
  • ipv6 addressWORD
  • ipv6 addressautoconfig
  • ipv6 addressdhcp

  • Specifies a global IPv6 address. Specify only the network prefix; the last 64 bits are automatically computed from the switch MAC address.

  • Specifies a link-local address on the interface to be used instead of the automatically configured link-local address when IPv6 is enabled on the interface.

  • Automatically configures an IPv6 link-local address on the interface, and enables the interface for IPv6 processing. The link-local address can only be used to communicate with nodes on the same link.

Note

 

To remove all manually configured IPv6 addresses from an interface, use the no ipv6 address interface configuration command without arguments.

Step 9

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 10

Use one of the following:

  • show interface interface-id
  • show ip interface interface-id
  • show ipv6 interface interface-id

Verifies your entries.

Step 11

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring Recursive DNS Server (RDNSS)

You can configure up to eight DNS servers to advertise with Router Advertisement. You can also remove one or more DNS servers from the advertising list by using the no form of the command.

Before you begin

Ensure that you are in the correct VDC (or use the switchto vdc command).

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode. Enter the password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface ethernet number

Example:

Device(config)# interface ethernet 3/3

Enters interface configuration mode.

Step 4

ipv6 nd ra dns server ipv6-addr [rdnss-life | infinite] sequence sequence-num

Example:

Device(config-if)# ipv6 nd ra dns server 1::1 1000 sequence 0

Configures the recursive DNS server. You can specify the life time and the sequence of the server.

Step 5

show ipv6 nd ra dns server [interface interface]

Example:

Device(config-if)# show ipv6 nd ra dns server

(Optional) Displays the configured RDNSS list.

Step 6

ipv6 nd ra dns server suppress

Example:

Device(config-if)# ipv6 nd ra dns server suppress

(Optional) Disables the configured server list.

Configuring Default Router Preference

Router advertisement messages are sent with the default router preference (DRP) configured by the ipv6 nd router-preference interface configuration command. If no DRP is configured, RAs are sent with a medium preference.

A DRP is useful when two routers on a link might provide equivalent, but not equal-cost routing, and policy might dictate that hosts should prefer one of the routers.

For more information about configuring DRP for IPv6, see the “Implementing IPv6 Addresses and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.

Beginning in privileged EXEC mode, follow these steps to configure a DRP for a router on an interface.

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface interface-id

Example:

Device(config)# interface gigabitethernet 1/0/1

Enters interface configuration mode and identifies the Layer 3 interface on which you want to specify the DRP.

Step 4

ipv6 nd router-preference {high | medium | low}

Example:

Device(config-if)# ipv6 nd router-preference medium

Specifies a DRP for the router on the switch interface.

Step 5

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 6

show ipv6 interface

Example:

Device# show ipv6 interface

Verifies the configuration.

Step 7

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

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.

To change the ICMP rate-limiting parameters, perform this procedure:

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 icmp error-interval interval [bucketsize]

Example:

Device(config)# ipv6 icmp error-interval 50 20

Configures the interval and bucket size for IPv6 ICMP error messages:

  • interval —The interval (in milliseconds) between tokens being added to the bucket. The range is from 0 to 2147483647 milliseconds.

  • bucketsize —(Optional) The maximum number of tokens stored in the bucket. The range is from 1 to 200.

Step 4

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 5

show ipv6 interface [interface-id]

Example:

Device# show ipv6 interface gigabitethernet0/1

Verifies your entries.

Step 6

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring Cisco Express Forwarding and distributed Cisco Express Forwarding for IPv6

Cisco Express Forwarding is a Layer 3 IP switching technology to improve network performance. Cisco Express Forwarding implements an advanced IP look-up and forwarding algorithm to deliver maximum Layer 3 switching performance. It is less CPU-intensive than fast-switching route-caching, allowing more CPU processing power to be dedicated to packet forwarding. IPv4 Cisco Express Forwarding and distributed Cisco Express Forwarding are enabled by default. IPv6 Cisco Express Forwarding and distributed Cisco Express Forwarding are disabled by default, but automatically enabled when you configure IPv6 routing.

IPv6 Cisco Express Forwarding and distributed Cisco Express Forwarding are automatically disabled when IPv6 routing is unconfigured. IPv6 Cisco Express Forwarding and distributed Cisco Express Forwarding cannot disabled through configuration. You can verify the IPv6 state by entering the show ipv6 cef command in privileged EXEC mode.

To route IPv6 unicast packets, you must first globally configure forwarding of IPv6 unicast packets by using the ipv6 unicast-routing global configuration command, and you must configure an IPv6 address and IPv6 processing on an interface by using the ipv6 address command in interface configuration mode.

For more information about configuring Cisco Express Forwarding and distributed Cisco Express Forwarding, see Cisco IOS IPv6 Configuration Library on Cisco.com.

Configuring Static Routing for IPv6

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.

To configure static IPv6 routing, perform this procedure:

Before you begin

You must enable routing by using the ip routing global configuration command, enable the forwarding of IPv6 packets by using the ipv6 unicast-routing command in global configuration mode, and enable IPv6 on at least one Layer 3 interface by configuring an IPv6 address on the interface.

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 route ipv6-prefix/prefix length {ipv6-address | interface-id [ipv6-address]} [administrative distance]

Example:

Device(config)# ipv6 route 2001:0DB8::/32 gigabitethernet2/0/1 130

Configures a static IPv6 route.

  • ipv6-prefix —The IPv6 network that is the destination of the static route. It can also be a hostname when static host routes are configured.

  • /prefix length— The length of the IPv6 prefix. 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). A slash mark must precede the decimal value.

  • ipv6-address —The IPv6 address of the next hop that can be used to reach the specified network. The IPv6 address of the next hop need not be directly connected; recursion is done to find the IPv6 address of the directly connected next hop. The address must be in the form documented in RFC 2373, specified in hexadecimal using 16-bit values between colons.

  • interface-id —Specifies direct static routes from point-to-point and broadcast interfaces. With point-to-point interfaces, there is no need to specify the IPv6 address of the next hop. With broadcast interfaces, you should always specify the IPv6 address of the next hop, or ensure that the specified prefix is assigned to the link, specifying a link-local address as the next hop. You can optionally specify the IPv6 address of the next hop to which packets are sent.

Note

 

You must specify an interface-id when using a link-local address as the next hop (the link-local next hop must also be an adjacent router).

  • administrative distance —(Optional) An administrative distance. The range is 1 to 254; the default value is 1, which gives static routes precedence over any other type of route except connected routes. To configure a floating static route, use an administrative distance greater than that of the dynamic routing protocol.

Step 4

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Step 5

Use one of the following:

  • show ipv6 static [ ipv6-address | ipv6-prefix/prefix length ] [interface interface-id ] [detail]][recursive] [detail]
  • show ipv6 route static [updated]

Example:

Device# show ipv6 static 2001:0DB8::/32 interface gigabitethernet2/0/1

or 

Device# show ipv6 route static

Verifies your entries by displaying the contents of the IPv6 routing table.

  • interface interface-id —(Optional) Displays only those static routes with the specified interface as an egress interface.

  • recursive —(Optional) Displays only recursive static routes. The recursive keyword is mutually exclusive with the interface keyword, but it can be used with or without the IPv6 prefix included in the command syntax.

  • detail —(Optional) Displays this additional information:

    • For valid recursive routes, the output path set, and maximum resolution depth.

    • For invalid routes, the reason why the route is not valid.

Step 6

copy running-config startup-config

Example:

Device# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Enabling IPv6 PBR on an Interface

To enable Policy-Based Routing (PBR) for IPv6, you must create a route map that specifies the packet match criteria and desired policy-route action. Then you associate the route map on the required interface. All packets arriving on the specified interface that match the match clauses will be subject to PBR.

In PBR, the set vrf command decouples the virtual routing and forwarding (VRF) instance and interface association and allows the selection of a VRF based on access control list (ACL)-based classification using existing PBR or route-map configurations. It provides a single router with multiple routing tables and the ability to select routes based on ACL classification. The router classifies packets based on ACL, selects a routing table, looks up the destination address, and then routes the packet.

To enable PBR for IPv6, perform this procedure:

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

route-map map-tag [permit | deny ] [sequence-number ]

Example:

Device(config)# route-map rip-to-ospf permit

Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing, and enters route-map configuration mode.

Step 4

Do one of the following:

  • match length minimum-length maximum-length
  • match ipv6 address {prefix-list prefix-list-name | access-list-name }

Example:

Device(config-route-map)# match length 3 200

Example:

Device(config-route-map)# match ipv6 address marketing

Specifies the match criteria.

  • You can specify any or all of the following:
    • Matches the Level 3 length of the packet.
    • Matches a specified IPv6 access list.
    • If you do not specify a match command, the route map applies to all packets.

Step 5

Do one of the following:

  • set ipv6 next-hop global-ipv6-address [global-ipv6-address... ]
  • set ipv6 default next-hop global-ipv6-address [global-ipv6-address... ]

Example:

Device(config-route-map)# set ipv6 next-hop 2001:DB8:2003:1::95

Example:

Device(config-route-map)# set ipv6 default next-hop 2001:DB8:2003:1::95

Specifies the action or actions to take on the packets that match the criteria.

  • You can specify any or all of the following:
    • Sets next hop to which to route the packet (the next hop must be adjacent).
    • Sets next hop to which to route the packet, if there is no explicit route for this destination.

Step 6

exit

Example:

Device(config-route-map)# exit

Exits route-map configuration mode and returns to global configuration mode.

Step 7

interface type number

Example:

Device(config)# interface FastEthernet 1/0

Specifies an interface type and number, and places the router in interface configuration mode.

Step 8

ipv6 policy route-map route-map-name

Example:

Device(config-if)# ipv6 policy-route-map interactive

Identifies a route map to use for IPv6 PBR on an interface.

Step 9

end

Example:

Device(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Enabling Local PBR for IPv6

Packets that are generated by the device are not normally policy routed. Perform this task to enable local IPv6 policy-based routing (PBR) for such packets, indicating which route map the device should use.

To enable Local PBR for IPv6, perform this procedure:

Procedure

  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 local policy route-map route-map-name

Example:

Device(config)# ipv6 local policy route-map pbr-src-90

Configures IPv6 PBR for packets generated by the device.

Step 4

end

Example:

Device(config)# end

Returns to privileged EXEC mode.

Displaying IPv6

For complete syntax and usage information on these commands, see the Cisco IOS command reference publications.

Table 2. Command for Monitoring IPv6

Command

Purpose

show ipv6 access-list

Displays a summary of access lists.

show ipv6 cef

Displays Cisco Express Forwarding for IPv6.

show ipv6 interface interface-id

Displays IPv6 interface status and configuration.

show ipv6 mtu

Displays IPv6 MTU per destination cache.

show ipv6 neighbors

Displays IPv6 neighbor cache entries.

show ipv6 prefix-list

Displays a list of IPv6 prefix lists.

show ipv6 protocols

Displays a list of IPv6 routing protocols on the switch.

show ipv6 rip

Displays IPv6 RIP routing protocol status.

show ipv6 route

Displays IPv6 route table entries.

show ipv6 static

Displays IPv6 static routes.

show ipv6 traffic

Displays IPv6 traffic statistics.

Configuration Examples for IPv6 Unicast Routing

The following sections shows the various configuration examples available for IPv6 Unicast Routing

Example: Configuring IPv4 and IPv6 Protocol Stacks

This example shows how to enable IPv4 and IPv6 routing on an interface. 

Device> enable
Device# configure terminal
Device(config)# ip routing
Device(config)# ipv6 unicast-routing
Devoce(config)# interface fastethernet1/0/11
Device(config-if)# no switchport
Device(config-if)# ip address 192.168.99.1 255.255.255.0
Device(config-if)# ipv6 address 2001:0DB8:c18:1::/64 eui 64
Device(config-if)# end

Example: Configuring RDNSS

The following example shows how to configure Recursive DNS Server list on Ethernet 3/3 and verify the same.

Device> enable
Device# configure terminal
Device(config)# interface ethernet 3/3
Device(config-if)# ipv6 nd ra dns server 1::1 1000 sequence 0
Device(config-if)# ipv6 nd ra dns server 2::1 infinite sequence 1
Device(config-if)# exit

Device(config)# show ipv6 nd ra dns server

Recursive DNS Server List on: mgmt0
Suppress DNS Server List: No
Recursive DNS Server List on: Ethernet3/3
  Suppress DNS Server List: No
  DNS Server 1: 1::1 Lifetime:1000 seconds Sequence:0
  DNS Server 2: 2::1 Infinite Sequence:1

Example: Configuring DNSSL

The following example shows how to configure DNS Search list on Ethernet 3/3 and verify the same.

Device> enable
Device# configure terminal
Device(config)# interface ethernet 3/3
Device(config-if)# ipv6 nd ra dns search-list cisco.com 100 sequence 1
Device(config-if)# ipv6 nd ra dns search-list ind.cisco.com 100 sequence 2
Device(config-if)# exit

Device(config)# show ipv6 nd ra dns search-list 

DNS Search List on: mgmt0
Suppress DNS Search List: No
 DNS Search List on: Ethernet3/3
  Suppress DNS Search List: No
  DNS Server 1:cisco.com 100 Sequence:1
  DNS Server 2:ind.cisco.com 100 Sequence:2

Example: Configuring Default Router Preference

This example shows how to configure a DRP of high for the router on an interface. 

Device> enable
Device# configure terminal
Device(config)# interface gigabitethernet1/0/1
Device(config-if)# ipv6 nd router-preference high
Device(config-if)# end

Example: Configuring IPv6 ICMP Rate Limiting

This example shows how to configure an IPv6 ICMP error message interval of 50 milliseconds and a bucket size of 20 tokens.

Device> enable
Device# configure terminal
Device(config)#ipv6 icmp error-interval 50 20

Example: Configuring Static Routing for IPv6

This example shows how to configure a floating static route to an interface with an administrative distance of 130:

Device> enable
Device# configure terminal
Device(config)# ipv6 route 2001:0DB8::/32 gigabitethernet 0/1 130

Example: Enabling PBR on an Interface

In the following example, a route map named pbr-dest-1 is created and configured, specifying packet match criteria and desired policy-route action. PBR is then enabled on GigabitEthernet interface 0/0/1. 

Device> enable
Device# configure terminal
Device(config)# ipv6 access-list match-dest-1
Device(config)# permit ipv6 any 2001:DB8:2001:1760::/32
Device(config)# route-map pbr-dest-1 permit 10
Device(config)# match ipv6 address match-dest-1
Device(config)# set interface GigabitEthernet 0/0/0
Device(config)# interface GigabitEthernet0/0/1
Device(config-if)# ipv6 policy-route-map interactive

Example: Enabling Local PBR for IPv6

In the following example, packets with a destination IPv6 address that match the IPv6 address range allowed by access list pbr-src-90 are sent to the device at IPv6 address 2001:DB8:2003:1::95: 

Device> enable
Device# configure terminal
Device(config)# ipv6 access-list src-90
Device(config)# permit ipv6 host 2001:DB8:2003::90 2001:DB8:2001:1000::/64
Device(config)# route-map pbr-src-90 permit 10
Device(config)# match ipv6 address src-90
Device(config)# set ipv6 next-hop 2001:DB8:2003:1::95
Device(config)# ipv6 local policy route-map pbr-src-90

Example: Displaying IPv6

This is an example of the output from the show ipv6 interface command: 

Device> enable
Device# show ipv6 interface
Vlan1 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::20B:46FF:FE2F:D940
  Global unicast address(es):
    3FFE:C000:0:1:20B:46FF:FE2F:D940, subnet is 3FFE:C000:0:1::/64 [EUI]
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::1:FF2F:D940
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  ND advertised reachable time is 0 milliseconds
  ND advertised retransmit interval is 0 milliseconds
  ND router advertisements are sent every 200 seconds
  ND router advertisements live for 1800 seconds
<output truncated>

Additional References

Standards and RFCs

Standard/RFC Title
RFC 5453

Reserved IPv6 Interface Identifiers
RFC 4292

IP Forwarding Table
RFC 4293

Management Information Base for the Internet Protocol (IP)

Feature History for IPv6 Unicast Routing

This table provides release and related information for the features explained in this module.

These features are available in all the releases subsequent to the one they were introduced in, unless noted otherwise.

Release

Feature

Feature Information

Cisco IOS XE Everest 16.5.1a

IPv6 Unicast Routing

IPv4 users can move to IPv6 and receive services such as end-to-end security, quality of service (QoS), and globally unique addresses.

Cisco IOS XE Fuji 16.8.1a

IPv6 Unicast Routing

Support for this feature was introduced only on the C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches.

Cisco IOS XE Gibraltar 16.11.1

RFC 5453

Support for RFC 5453 was introduced.

RFC 4292

Support for RFC 4292 was introduced.

RFC 4293

Support for RFC 4293 was introduced.

IPv6 Router Advertisement Options for DNS Configuration

IPv6 Router Advertisement provides options to allow IPv6 hosts to perform automatic DNS configuration.

Use the Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn.