- IP over IPv6 Tunnels
- Configuring LAN Interfaces
- Configuring Serial Interfaces
- Circuit Emulation over IP
- Lossless Compression R1 ATM Cell Switching and External BITS Clocking Source
- Minimal Disruptive Restart of VIP Cards
- Rate Based Satellite Control Protocol
- Configuring Virtual Interfaces
- Implementing Tunnels
- Tunnel Route Selection
- MPLS VPN over mGRE
- IP Tunnel MIBs
- Managing Dial Shelves
- Router-Shelf Redundancy for the Cisco AS5800
- Route-Switch-Controller Handover Redundancy on the Cisco AS5850
- Route Processor Redundancy Plus
- IPv6 Automatic 6to4 Tunnels
- IPv6 Automatic IPv4-Compatible Tunnels
- IPv6 GRE Tunnels in CLNS Networks
- ISATAP Tunnel Support for IPv6
- Manually Configured IPv6 over IPv4 Tunnels
- IPv6 over IPv4 GRE Tunnels
IPv6 GRE Tunnels in CLNS Networks
GRE tunneling of IPv4 and IPv6 packets through CLNS networks enables Cisco CTunnels to interoperate with networking equipment from other vendors.
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 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 IPv6 GRE Tunnels in CLNS Networks
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)
| Figure 1 | Overlay Tunnels |
 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 |
|||
|---|---|---|---|---|
| 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 CLNS Tunnel Support for IPv4 and IPv6 Packets
GRE tunneling of IPv4 and IPv6 packets through CLNS networks enables Cisco CLNS Tunnels (CTunnels) to interoperate with networking equipment from other vendors. This feature provides compliance with RFC 3147.
The optional GRE services defined in header fields, such as checksums, keys, and sequencing, are not supported. Any packet received requesting such services will be dropped.
Configuration Examples for IPv6 GRE Tunnels in CLNS Networks
Example: Configuring CTunnels in GRE Mode to Carry IPv6 Packets in CLNS
The following example configures a GRE CTunnel running both IS-IS and IPv6 traffic between Router A and Router B in a CLNS network. The ctunnel mode gre command allows tunneling between Cisco and third-party networking devices and carries both IPv4 and IPv6 traffic.
The ctunnel mode gre command provides a method of tunneling that is compliant with RFC 3147 and allows tunneling between Cisco equipment and third-party networking devices.
Router A
ipv6 unicast-routing clns routing interface ctunnel 102 ipv6 address 2001:DB8:1111:2222::1/64 ctunnel destination 49.0001.2222.2222.2222.00 ctunnel mode gre interface Ethernet0/1 clns router isis router isis net 49.0001.1111.1111.1111.00
Router B
ipv6 unicast-routing clns routing interface ctunnel 201 ipv6 address 2001:DB8:1111:2222::2/64 ctunnel destination 49.0001.1111.1111.1111.00 ctunnel mode gre interface Ethernet0/1 clns router isis router isis net 49.0001.2222.2222.2222.00
To turn off GRE mode and restore the CTunnel to the default Cisco encapsulation routing only between endpoints on Cisco equipment, use either the no ctunnel mode command or the ctunnel mode cisco command. The following example shows the same configuration modified to transport only IPv4 traffic.
Additional References
Related Documents
| Related Topic | Document Title |
|---|---|
| IPv6 addressing and connectivity |
IPv6 Configuration Guide |
| Cisco IOS commands |
|
| IPv6 commands |
|
| 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: |
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. |
Feature Information for IPv6 GRE Tunnels in CLNS Networks
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 IPv6 GRE Tunnels in CLNS Networks |
| Feature Name | Releases | Feature Information |
|---|---|---|
| CLNS Support for GRE Tunneling of IPv4 and IPv6 |
12.2(25)S 12.2(33)SRA 12.3(7)T |
GRE tunneling of IPv4 and IPv6 packets through CLNS networks enables Cisco CTunnels to interoperate with networking equipment from other vendors. The following commands were introduced or modified: ctunnel mode. |
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
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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