IP over IPv6 Tunnels [Support]

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Toolkit and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About IP over IPv6 Tunnels

Overlay Tunnels for IPv6
IPv6 Manually Configured Tunnels
GRE IPv4 Tunnel Support for IPv6 Traffic
GRE Support over IPv6 Transport

Overlay Tunnels for IPv6

Overlay tunneling encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure (a core network or the Internet (see the figure below). By using overlay tunnels, you can communicate with isolated IPv6 networks without upgrading the IPv4 infrastructure between them. Overlay tunnels can be configured between border routers or between a border router and a host; however, both tunnel endpoints must support both the IPv4 and IPv6 protocol stacks. IPv6 supports the following types of overlay tunneling mechanisms:

Manual
Generic routing encapsulation (GRE)
IPv4-compatible
6to4
Intrasite Automatic Tunnel Addressing Protocol (ISATAP)

Figure 1

Overlay Tunnels

Note

Overlay tunnels reduce the maximum transmission unit (MTU) of an interface by 20 octets (assuming the basic IPv4 packet header does not contain optional fields). A network using overlay tunnels is difficult to troubleshoot. Therefore, overlay tunnels connecting isolated IPv6 networks should not be considered as a final IPv6 network architecture. The use of overlay tunnels should be considered as a transition technique toward a network that supports both the IPv4 and IPv6 protocol stacks or just the IPv6 protocol stack.

Use the table below to help you determine which type of tunnel you want to configure to carry IPv6 packets over an IPv4 network.

Table 1

Suggested Usage of Tunnel Types to Carry IPv6 Packets over an IPv4 Network

Tunneling Type	Suggested Usage	Usage Notes
Manual	Simple point-to-point tunnels that can be used within a site or between sites	Can carry IPv6 packets only.
GRE- and IPv4- compatible	Simple point-to-point tunnels that can be used within a site or between sites	Can carry IPv6, Connectionless Network Service (CLNS), and many other types of packets.
IPv4- compatible	Point-to-multipoint tunnels	Uses the ::/96 prefix. We do not now recommend using this tunnel type.
6to4	Point-to-multipoint tunnels that can be used to connect isolated IPv6 sites	Sites use addresses from the 2002::/16 prefix.
6RD	IPv6 service is provided to customers over an IPv4 network by using encapsulation of IPv6 in IPv4.	Prefixes can be from the SP's own address block.
ISATAP	Point-to-multipoint tunnels that can be used to connect systems within a site	Sites can use any IPv6 unicast addresses.

Individual tunnel types are discussed in detail in this document. We recommend that you review and understand the information about the specific tunnel type that you want to implement. When you are familiar with the type of tunnel you need, see the table below for a summary of the tunnel configuration parameters that you may find useful.

Table 2

Tunnel Configuration Parameters by Tunneling Type

Tunneling Type	Tunnel Configuration Parameter
Tunneling Type	Tunnel Mode	Tunnel Source	Tunnel Destination	Interface Prefix or Address
Manual	ipv6ip	An IPv4 address, or a reference to an interface on which IPv4 is configured.	An IPv4 address.	An IPv6 address.
GRE/IPv4	gre ip		An IPv4 address.	An IPv6 address.
IPv4- compatible	ipv6ip auto-tunnel		Not required. These are all point-to-multipoint tunneling types. The IPv4 destination address is calculated, on a per-packet basis, from the IPv6 destination.	Not required. The interface address is generated as ::tunnel-source/96.
6to4	ipv6ip 6to4			An IPv6 address. The prefix must embed the tunnel source IPv4 address
6RD	ipv6ip 6rd			An IPv6 address.
ISATAP	ipv6ip isatap			An IPv6 prefix in modified eui-64 format. The IPv6 address is generated from the prefix and the tunnel source IPv4 address.

IPv6 Manually Configured Tunnels

A manually configured tunnel is equivalent to a permanent link between two IPv6 domains over an IPv4 backbone. The primary use is for stable connections that require regular secure communication between two edge routers or between an end system and an edge router, or for connection to remote IPv6 networks.

An IPv6 address is manually configured on a tunnel interface, and manually configured IPv4 addresses are assigned to the tunnel source and the tunnel destination. The host or router at each end of a configured tunnel must support both the IPv4 and IPv6 protocol stacks. Manually configured tunnels can be configured between border routers or between a border router and a host. Cisco Express Forwarding switching can be used for IPv6 manually configured tunnels, or Cisco Express Forwarding switching can be disabled if process switching is needed.

GRE IPv4 Tunnel Support for IPv6 Traffic

IPv6 traffic can be carried over IPv4 GRE tunnels using the standard GRE tunneling technique that is designed to provide the services necessary to implement any standard point-to-point encapsulation scheme. As in IPv6 manually configured tunnels, GRE tunnels are links between two points, with a separate tunnel for each link. The tunnels are not tied to a specific passenger or transport protocol, but in this case, carry IPv6 as the passenger protocol with the GRE as the carrier protocol and IPv4 or IPv6 as the transport protocol.

The primary use of GRE tunnels is for stable connections that require regular secure communication between two edge routers or between an edge router and an end system. The edge routers and the end systems must be dual-stack implementations.

GRE Support over IPv6 Transport

GRE has a protocol field that identifies the passenger protocol. GRE tunnels allow Intermediate System-to-Intermediate System (IS-IS) or IPv6 to be specified as a passenger protocol, which allows both IS-IS and IPv6 traffic to run over the same tunnel. If GRE did not have a protocol field, it would be impossible to distinguish whether the tunnel was carrying IS-IS or IPv6 packets. The GRE protocol field is why it is desirable that you tunnel IS-IS and IPv6 inside GRE.

Configuring Manual IPv6 Tunnels

Before You Begin

With manually configured IPv6 tunnels, an IPv6 address is configured on a tunnel interface, and manually configured IPv4 addresses are assigned to the tunnel source and the tunnel destination. The host or router at each end of a configured tunnel must support both the IPv4 and IPv6 protocol stacks.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface tunnel tunnel-number

4. ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

5. tunnel source {ip-address| interface-t ype interface-number}

6. tunnel destination ip-address

7. tunnel mode ipv6ip [6rd | 6to4 | auto-tunnel | isatap

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface tunnel tunnel-number

Example:

Router(config)# interface tunnel 0

Specifies a tunnel interface and number, and enters interface configuration mode.

Step 4

ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

Example:

Router(config-if)# ipv6 address 3ffe:b00:c18:1::3/127

Specifies the IPv6 network assigned to the interface and enables IPv6 processing on the interface.

Note

Refer to the Implementing IPv6 Addressing and Basic Connectivity module for more information on configuring IPv6 addresses.

Step 5

tunnel source {ip-address| interface-t ype interface-number}

Example:

Router(config-if)# tunnel source gigabitethernet 0/0/0

Specifies the source IPv4 address or the source interface type and number for the tunnel interface.

If an interface is specified, the interface must be configured with an IPv4 address.

Step 6

tunnel destination ip-address

Example:

Router(config-if)# tunnel destination 192.168.30.1

Specifies the destination IPv4 address or hostname for the tunnel interface.

Step 7

tunnel mode ipv6ip [6rd | 6to4 | auto-tunnel | isatap

Example:

Router(config-if)# tunnel mode ipv6ip

Specifies a manual IPv6 tunnel.

Note

The tunnel mode ipv6ip command specifies IPv6 as the passenger protocol and IPv4 as both the encapsulation and transport protocol for the manual IPv6 tunnel.

The auto-tunnel keyword is not supported on Cisco ASR 1000 series routers.

Configuring GRE IPv6 Tunnels

GRE tunnels can be configured to run over an IPv6 network layer and to transport IPv6 packets in IPv6 tunnels and IPv4 packets in IPv6 tunnels.

Before You Begin

When GRE IPv6 tunnels are configured, IPv6 addresses are assigned to the tunnel source and the tunnel destination. The tunnel interface can have either IPv4 or IPv6 addresses assigned (this is not shown in the task). The host or router at each end of a configured tunnel must support both the IPv4 and IPv6 protocol stacks.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface tunnel tunnel-number

4. ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

5. tunnel source {ip-address | ipv6-address | interface-type interface-number}

6. tunnel destination {host-name | ip-address | ipv6-address}

7. tunnel mode {aurp | cayman | dvmrp | eon | gre| gre multipoint | gre ipv6 | ipip [decapsulate-any] | iptalk | ipv6 | mpls | nos

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface tunnel tunnel-number

Example:

Router(config)# interface tunnel 0

Specifies a tunnel interface and number, and enters interface configuration mode.

Step 4

ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

Example:

Router(config-if)# ipv6 address 3ffe:b00:c18:1::3/127

Specifies the IPv6 network assigned to the interface and enables IPv6 processing on the interface.

Step 5

tunnel source {ip-address | ipv6-address | interface-type interface-number}

Example:

Router(config-if)# tunnel source gigabitethernet 0/0/0

Specifies the source IPv4 address or the source interface type and number for the tunnel interface.

If an interface is specified, the interface must be configured with an IPv4 address.

Step 6

tunnel destination {host-name | ip-address | ipv6-address}

Example:

Router(config-if)# tunnel destination 2001:DB8:1111:2222::1/64

Specifies the destination IPv4 address or hostname for the tunnel interface.

Step 7

tunnel mode {aurp | cayman | dvmrp | eon | gre| gre multipoint | gre ipv6 | ipip [decapsulate-any] | iptalk | ipv6 | mpls | nos

Example:

Router(config-if)# tunnel mode gre ipv6

Specifies a GRE IPv6 tunnel.

Note

The tunnel mode gre ipv6command specifies GRE as the encapsulation protocol for the tunnel.

Configuration Examples for IP over IPv6 Tunnels

Example: Configuring IPv4-Compatible IPv6 Tunnels

Example: Configuring IPv4-Compatible IPv6 Tunnels

The following example configures an IPv4-compatible IPv6 tunnel that allows Border Gateway Protocol (BGP) to run between a number of routers without having to configure a mesh of manual tunnels. Each router has a single IPv4-compatible tunnel, and multiple BGP sessions can run over each tunnel, one to each neighbor. GigabitEthernet interface 0/0/0 is used as the tunnel source. The tunnel destination is automatically determined by the IPv4 address in the low-order 32 bits of an IPv4-compatible IPv6 address. Specifically, the IPv6 prefix 0:0:0:0:0:0 is concatenated to an IPv4 address (in the format 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D) to create the IPv4-compatible IPv6 address. GigabitEthernet interface 0/0/0 is configured with a global IPv6 address and an IPv4 address (the interface supports both the IPv6 and IPv4 protocol stacks).

Multiprotocol BGP is used in the example to exchange IPv6 reachability information with the peer 10.67.0.2. The IPv4 address of GigabitEthernet interface 0/0/0 is used in the low-order 32 bits of an IPv4-compatible IPv6 address and is also used as the next-hop attribute. Using an IPv4-compatible IPv6 address for the BGP neighbor allows the IPv6 BGP session to be automatically transported over an IPv4-compatible tunnel.

interface tunnel 0
 tunnel source GigabitEthernet 0/0/0
 tunnel mode ipv6ip auto-tunnel
interface Gigabitethernet 0/0/0
 ip address 10.27.0.1 255.255.255.0
 ipv6 address 3000:2222::1/64
router bgp 65000
 no synchronization
 no bgp default ipv4-unicast
neighbor ::10.67.0.2 remote-as 65002
address-family ipv6
 neighbor ::10.67.0.2 activate
 neighbor ::10.67.0.2 next-hop-self
 network 2001:2222:d00d:b10b::/64

Additional References

Standards and RFCs

Standard/RFC	Title
RFCs for IPv6	IPv6 RFCs

MIBs

MIB

MIBs Link

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

Technical Assistance

Description	Link
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.	http://www.cisco.com/cisco/web/support/index.html

Feature Information for IP over IPv6 Tunnels

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 3

Feature Information for IP over IPv6 Tunnels

Feature Name

Releases

Feature Information

IP over IPv6 Tunnels

Cisco IOS XE Release 2.1

IPv6 supports this feature.

The following commands were introduced or modified: tunnel destination, tunnel mode, tunnel mode ipv6ip, tunnel source.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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