IPv6 over IPv4 GRE Tunnels
Finding Feature Information
Information About IPv6 over IPv4 GRE Tunnels
- Overlay Tunnels for IPv6
- GRE IPv4 Tunnel Support for IPv6 Traffic
How to Configure IPv6 over IPv4 GRE Tunnels
- Configuring GRE on IPv6 Tunnels
Configuration Examples for IPv6 over IPv4 GRE Tunnels
- Example GRE Tunnel Running IS-IS and IPv6 Traffic
- Example: Tunnel Destination Address for IPv6 Tunnel
Additional References
Feature Information for IPv6 over IPv4 GRE Tunnels

IPv6 over IPv4 GRE 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.

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 Search Tool 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.

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 IPv6 over IPv4 GRE Tunnels

Overlay Tunnels for IPv6

Overlay tunneling encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure (a core network or 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 devices or between a border device 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)

Note

Overlay tunnels reduce the maximum transmission unit (MTU) of an interface by 20 octets (assuming that the basic IPv4 packet header does not contain optional fields). A network that uses overlay tunnels is difficult to troubleshoot. Therefore, overlay tunnels that connect isolated IPv6 networks should not be considered 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 that 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 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.

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 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 devices or between an edge device and an end system. The edge devices and the end systems must be dual-stack implementations.

How to Configure IPv6 over IPv4 GRE Tunnels

Configuring GRE on IPv6 Tunnels

GRE tunnels can be configured to run over an IPv6 network layer and to transport IPv4 and IPv6 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 addresses or IPv6 addresses assigned (this is not shown in the task). The host or device at each end of a configured tunnel must support both the IPv4 and IPv6 protocol stacks.

SUMMARY STEPS

enable
configure terminal
interface tunnel tunnel-number
Enter one of the following commands:

ipv6 address {ipv6-address/ prefix-length | prefix-name sub-bits/ prefix-length}
ipv6 address ipv6-prefix/ prefix-length [eui-64 ]

tunnel source {ip-address | ipv6-address | interface-type interface-number}
tunnel destination {hostname | ip-address | ipv6-address}
tunnel mode {aurp | cayman | dvmrp | eon | gre | gre multipoint | gre ipv6 | ipip [decapsulate-any ] | iptalk | ipv6 | mpls | nos }
end

DETAILED STEPS

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 tunnel tunnel-number

Example:


Device(config)# interface tunnel 0

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

Step 4

Enter one of the following commands:

ipv6 address {ipv6-address/ prefix-length | prefix-name sub-bits/ prefix-length}
ipv6 address ipv6-prefix/ prefix-length [eui-64 ]

Example:


Device(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.

If you specify the eui-64 keyword, the software configures an IPv6 address for an interface and enables IPv6 processing on the interface using an EUI-64 interface ID in the low-order 64 bits of the address.

Step 5

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

Example:


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

Specifies the source IPv4 address, IPv6 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 {hostname | ip-address | ipv6-address}

Example:


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

Specifies the destination IPv4 address, IPv6 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:


Device(config-if)# tunnel mode gre ipv6

Specifies a GRE IPv6 tunnel.

Note

The tunnel mode gre ipv6 command specifies GRE as the encapsulation protocol for the tunnel.

Step 8

end

Example:


Device(config-if)# end

Returns to privileged EXEC mode.

Configuration Examples for IPv6 over IPv4 GRE Tunnels

Example GRE Tunnel Running IS-IS and IPv6 Traffic

The following example configures a GRE tunnel running both IS-IS and IPv6 traffic between Router A and Router B:

Router A Configuration


ipv6 unicast-routing
clns routing
!
interface tunnel 0
 no ip address
 ipv6 address 3ffe:b00:c18:1::3/127
 ipv6 router isis 
 tunnel source GigabitEthernet 0/0/0
 tunnel destination 2001:DB8:1111:2222::1/64
 tunnel mode gre ipv6
!
interface GigabitEthernet0/0/0
 ip address 10.0.0.1 255.255.255.0
!
router isis 
 net 49.0000.0000.000a.00

Router B Configuration


ipv6 unicast-routing
clns routing
!
interface tunnel 0
 no ip address
 ipv6 address 3ffe:b00:c18:1::2/127
 ipv6 router isis 
 tunnel source GigabitEthernet 0/0/0
 tunnel destination 2001:DB8:1111:2222::2/64
 tunnel mode gre ipv6
!
interface GigabitEthernet0/0/0
 ip address 10.0.0.2 255.255.255.0
!
router isis 
 net 49.0000.0000.000b.00
 address-family ipv6
 redistribute static
 exit-address-family

Example: Tunnel Destination Address for IPv6 Tunnel


Router(config
)
# 
interface Tunnel0
Router(config
-if)
# 
ipv6 address 2001:1:1::1/48
Router(config
-if)
# 
tunnel source GigabitEthernet 0/0/0
Router(config
-if)
# 
tunnel destination 10.0.0.2
Router(config
-if)
# 
tunnel mode gre ipv6
Router(config
-if)
# 
exit
!
Router(config
)
# 
interface GigabitEthernet0/0/0
Router(config
-if)
# 
ip address 10.0.0.1 255.255.255.0
Router(config
-if)
# 
exit
!
Router(config
)
# 
ipv6 unicast-routing
Router(config
)
# 
router isis
 
Router(config
)
# 
net 49.0000.0000.000a.00

Additional References

Related Topic	Document Title
IPv6 addressing and connectivity	IPv6 Configuration Guide
Cisco IOS commands	Cisco IOS Master Commands List, All Releases
IPv6 commands	Cisco IOS IPv6 Command Reference
Cisco IOS IPv6 features	Cisco IOS IPv6 Feature Mapping

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 IPv6 over IPv4 GRE 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.

Table 3. Feature Information for IPv6 over IPv4 GRE Tunnels
Feature Name	Releases	Feature Information
IPv6 over IPv4 GRE Tunnels	Cisco IOS XE Release 2.1	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 following commands were introduced or modified: tunnel destination , tunnel mode ipv6ip , tunnel source .

Interface and Hardware Component Configuration Guide, Cisco IOS XE Everest 16.6

Bias-Free Language

Book Title

Interface and Hardware Component Configuration Guide, Cisco IOS XE Everest 16.6

Chapter Title