Cisco IOS Software Releases 12.3 T

Table Of Contents

CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

Contents

Prerequisites for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

Information About Tunneling IPv4 and IPv6 Packets over CLNS Networks

How to Configure CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

Configuring CTunnels in GRE Mode to Carry IPv4 and IPv6 Packets in CLNS Networks

Prerequisites

Restrictions

What to Do Next

Configuration Examples for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets

Configuring CTunnels in GRE mode to Carry IPv6 Packets in CLNS: Example

Where to Go Next

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

ctunnel mode

CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

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Support of the GRE tunnel mode allows Cisco CTunnels to transport IPv4 and IPv6 packets over CLNS-only networks in a manner that allows Cisco networking equipment to interoperate with networking equipment from other vendors. This feature provides compliance with RFC 3147.

History for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

Release	Modification
12.3(7)T	This feature was introduced.
12.2(25)S	This feature was integrated into Cisco IOS Release 12.2(25)S.
12.2(27)SBC	This feature was integrated into Cisco IOS Release 12.2(27)SBC.
12.2(33)SRA	This feature was integrated into Cisco IOS Release 12.2(33)SRA.

Finding Support Information for Platforms and Cisco IOS Software Images

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

•Information About Tunneling IPv4 and IPv6 Packets over CLNS Networks

•How to Configure CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

•Configuration Examples for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets

•Where to Go Next

•Additional References

•Command Reference

Prerequisites for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

Both ends of a CTunnel must be configured with the same mode for packets to be successfully delivered.

Information About Tunneling IPv4 and IPv6 Packets over CLNS Networks

Configuring the ctunnel gre mode command on a CTunnel interface enables IPv4 and IPv6 packets to be tunneled over CLNS in accordance with RFC 3147. Compliance with this RFC should allow interoperation between Cisco equipment and that of other vendors in which the same standard is implemented.

RFC 3147 specifies the use of GRE for tunneling packets. The implementation of this feature does not include support for GRE services defined in header fields, such as those used to specify checksums, keys, or sequencing. Any packets received which specify the use of these features will be dropped.

The default CTunnel mode continues to use the standard Cisco encapsulation which will tunnel only IPv4 packets. If you want to tunnel IPv6 packets you must use the new GRE encapsulation mode. Both ends of the tunnel must be configured with the same mode for either method to work.

How to Configure CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks

This section includes the following configuration task:

•Configuring CTunnels in GRE Mode to Carry IPv4 and IPv6 Packets in CLNS Networks

Configuring CTunnels in GRE Mode to Carry IPv4 and IPv6 Packets in CLNS Networks

This task explains how to configure a CTunnel in GRE mode to transport IPv4 and IPv6 packets in a CLNS network.

Prerequisites

•An IPv4 or IPv6 address is configured on a CTunnel interface, and manually configured CLNS addresses are assigned to the CTunnel destination.

•The host or router at each end of a configured CTunnel must support both the IPv4 and IPv6 protocol stacks.

•The CTunnel source and destination must both be configured to run in the same mode.

Restrictions

GRE services such as those used to specify checksums, keys, or sequencing are not supported. Packets requesting use of those features will be dropped.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface ctunnel interface-number

4. ip address ip-address

or

ipv6 address ipv6-prefix/prefix-length [eui-64]

5. ctunnel destination remote-nsap-address

6. ctunnel mode gre

7. exit

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 ctunnel interface-number Example: Router(config)# interface ctunnel 0	Creates a virtual interface to transport IPv4 or IPv6 packets over a CLNS CTunnel and enters interface configuration mode. The interface number must be unique for each CTunnel interface.
Step 4	ip address ip-address subnet-mask or ipv6 address ipv6-prefix/prefix-length [eui-64] Example: Router(config-if)# ipv6 address 3ffe:b00:c18:1::3/127	Specifies the IPv4 or IPv6 network assigned to the interface and enables IPv4 or IPv6 packet processing on the interface. Note Refer to the Implementing Basic Connectivity for IPv6 module for more information on configuring IPv6 addresses.
Step 5	ctunnel destination remote-nsap-address Example: Router(config-if)# ctunnel destination 192.168.30.1	Configures the destination parameter for the CTunnel. Specifies the destination network service access point (NSAP) address of the CTunnel, where the IP packets are extracted.
Step 6	ctunnel mode gre Example: Router(config-if)# ctunnel mode gre	Specifies a CTunnel running in GRE mode for both IPv4 and IPv6 traffic. Note The ctunnel mode gre command specifies GRE as the encapsulation protocol for the tunnel.
Step 7	exit Example: Router(config-if)# exit	Exits interface configuration mode and enters global configuration mode.

What to Do Next

To verify correct configuration of IPv4 or IPv6 over a CLNS CTunnel feature, perform the following steps:

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Step 1 On Router A, ping the IP address of the CTunnel interface of Router B.

Step 2 Step 2 On Router B, ping the IP address of the CTunnel interface of Router A.

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Configuration Examples for CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets

The following example shows how to configure a CTunnel which will carry IPv6 packets over a CLNS network.

•Configuring CTunnels in GRE mode to Carry IPv6 Packets in CLNS: Example

Configuring CTunnels in GRE mode to Carry IPv6 Packets in CLNS: Example

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 tunnelling between Cisco and third-party networking devices and carries both IPv4 and IPv6 traffic.

The ctunnel mode gre command provides a method of tunneling compliant with RFC 3147 and should allow tunneling between Cisco equipment and third-party networking devices.

Router A

ipv6 unicast-routing 

clns routing 

interface ctunnel 102 

 ipv6 address 2001:0DB8:1111:2222::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 2001:0DB8:1111:2222::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 the 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 Iv4 traffic:

Router A

ipv6 unicast-routing 

clns routing 

interface ctunnel 102 

 ip address 10.2.2.5 255.255.255.0 

 ctunnel destination 49.0001.2222.2222.2222.00 

 ctunnel mode cisco

interface Ethernet0/1 

 clns router isis 

router isis 

 net 49.0001.1111.1111.1111.00 

Router B

ip routing 

clns routing 

interface ctunnel 201 

 ip address 10.0.0.5 255.255.255.0 

 ctunnel destination 49.0001.1111.1111.1111.00 

 ctunnel mode cisco

interface Ethernet0/1 

 clns router isis 

router isis 

net 49.0001.2222.2222.2222.00

Where to Go Next

Refer to the Cisco IOS Network Protocols 3: CLNS for more information about CLNS and CTunnels.

Additional References

The following sections provide references related to CLNS Support for GRE Tunneling of IPv4 and IPv6 Packets in CLNS Networks.

Related Documents

Related Topic	Document Title
CLNS and CTunnels	Cisco
IPv6 and supported tunnels	Implementing Tunneling for IPv6

Standards

Standards	Title
None	—

MIBs

MIBs	MIBs Link
None	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

RFCs

RFCs	Title
RFC 3147	Generic Routing Encapsulation over CLNS Networks

Technical Assistance

Description	Link
The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.	http://www.cisco.com/techsupport

Command Reference

This section documents a modified command.

•ctunnel mode

ctunnel mode

To transport IPv4 and IPv6 packets over Connectionless Network Service (CLNS) tunnel (CTunnel), use the ctunnel mode command in interface configuration mode. To return the ctunnel to the default cisco mode, use the no form of this command.

ctunnel mode [gre | cisco]

no ctunnel mode

Syntax Description

gre	(Optional) Sets the ctunnel mode to Generic Routing Encapsulation (GRE) for transporting IPv6 packets over the CLNS network.
cisco	(Optional) Returns the ctunnel mode to the default cisco.

Command Default

Cisco encapsulation

Command Modes

Interface configuration

Command History

Release	Modification
12.3(7)T	This command was introduced.
12.2(25)S	This command was integrated into Cisco IOS Release 12.2(25)S.
12.2(28)SB	This command was integrated into Cisco IOS Release 12.2(28)SB.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SXH	This command was integrated into Cisco IOS Release 12.2(33)SXH.

Usage Guidelines

GRE tunneling of IPv4 and IPv6 packets through CLNS-only networks enables Cisco ctunnels to interoperate with networking equipment from other vendors. This feature provides compliance with RFC 3147, Generic Routing Encapsulation over CLNS Networks, which should allow interoperation between Cisco equipment and that of other vendors. in which the same standard is implemented.

RFC 3147 specifies the use of GRE when tunneling packets. The implementation of this feature does not include support for GRE header fields such as those used to specify checksums, keys, or sequencing. Any packets received which specify the use of these features will be dropped.

The default ctunnel mode continues to use the standard Cisco encapsulation. Both ends of the tunnel must be configured with the same mode for it to work. If you want to tunnel ipv6 packets you must use the new gre mode.

Examples

The following example configures a CTunnel from one router to another and shows the CTunnel destination set to 49.0001.1111.1111.1111.00. The ctunnel mode is set to gre to transport IPv6 packets.

interface ctunnel 301

 ipv6 address 2001:0DB8:1111:2222::2/64

 ctunnel destination 49.0001.1111.1111.1111.00

 ctunnel mode gre

Related Commands

Command	Description
clns routing	Enables routing of CLNS packets.
ctunnel destination	Specifies the destination for the CTunnel.
debug ctunnel	Displays debug messages for the IP over a CLNS Tunnel feature.
interface ctunnel	Creates a virtual interface to transport IP over a CLNS tunnel.
ip address	Sets a primary or secondary IP address for an interface.

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

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