Tunnel Route Selection
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Table Of Contents
Prerequisites for Tunnel Route Selection
Restrictions for Tunnel Route Selection
Information About Tunnel Route Selection
How to Configure Tunnel Route Selection
Configuring Tunnel Route Selection
Configuration Examples for Tunnel Route Selection
Example: Configuring Tunnel Route Selection
Feature Information for Tunnel Route Selection
Tunnel Route Selection
First Published: November 17, 2006Last Updated: October 02, 2009The Tunnel Route Selection feature allows the tunnel transport to be routed using a subset of the routing table. When there are equal-cost routes to a tunnel destination, normal tunnel transport behavior is to use one of the available routes chosen at random. The Tunnel Route Selection feature allows the explicit configuration of the outgoing interface for the tunnel transport.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see 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 for Tunnel Route Selection" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for Tunnel Route Selection
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Prerequisites for Tunnel Route Selection
Tunnel interfaces are configured.
Restrictions for Tunnel Route Selection
This feature is supported in the following tunnel modes only:
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This feature is not supported on a tunnel when the tunnel transport is a GRE Multipoint tunnel.
Supported Configuration
interface tunnel 0tunnel mode gre multipointtunnel route-via tunnel 1interface tunnel 1tunnel mode gre ipUnsupported Configuration
interface tunnel 0tunnel mode gre multipointtunnel route-via tunnel 1interface tunnel 1tunnel mode gre multipointInformation About Tunnel Route Selection
Tunnel Transport Behavior
The Tunnel Route Selection feature allows the tunnel transport to be routed using a subset of the routing table by specifying the outgoing interface of the tunnel transport.
The Tunnel Route Selection feature is not the same as an implementation of policy-based routing for the tunnel transport. The Tunnel Route Selection feature will forward traffic using only a subset of the route table, and it cannot introduce routing loops into the network.
Figure 1 compares default tunnel behavior with the Tunnel Route Selection behavior.
Figure 1 Tunnel Route Selection Traffic
How to Configure Tunnel Route Selection
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Configuring Tunnel Route Selection
Perform the following steps to specify the outgoing interface of the tunnel transport to route the tunnel transport using a subset of the routing table.
SUMMARY STEPS
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DETAILED STEPS
Troubleshooting Tips
To troubleshoot your configuration, use the debug tunnel route-via command in privileged EXEC mode. The following is sample output from the debug tunnel route-via command after the tunnel route-via command was used to route the tunnel transport explicitly using a subset of the routing table.
Router# debug tunnel route-viaTunnel route-via debugging is onRouter#*May 23 08:40:53.707: TUN-VIA: Tunnel0 candidate route-via Ethernet0/0, next hop 10.73.2.1*May 23 08:40:53.707: TUN-VIA: Tunnel0 route-via action is forward*May 23 08:41:03.719: TUN-VIA: Tunnel0 candidate route-via Ethernet0/0, next hop 10.73.2.1*May 23 08:41:03.719: TUN-VIA: Tunnel0 route-via action is forwardRouter# undebug tunnel route-viaTunnel route-via debugging is offWhat to Do Next
You can verify the tunnel route selection configuration. To verify your configuration, use the show interfaces tunnel command in privileged EXEC mode. The following example shows that the tunnel transport is routed using a subset of the routing table by specifying the outgoing interface of the tunnel transport.
Router# show running-config interface tunnel 0Building configuration...Current configuration : 147 bytes!interface Tunnel0ip unnumbered Loopback0tunnel source Loopback0tunnel destination 10.73.0.102tunnel route-via Ethernet0 preferredendRouter# show interfaces tunnel 0 | include route-viaTunnel route-via feature is on [Ethernet0, preferred]
Configuration Examples for Tunnel Route Selection
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Example: Configuring Tunnel Route Selection
The following example shows Tunnel 0 configured to use Ethernet interface 0 as its preferred outgoing transport interface. Traffic that exits the router using the tunnel 0 interface will be sent out of Ethernet interface 0 if there is a route to the tunnel destination out of Ethernet interface 0. If there is no route out of Ethernet interface 0, the traffic will be forwarded as if the Tunnel Route Selection feature were not configured.
If the tunnel route-via interface-type interface-number mandatory command is configured, and there is no route to the tunnel destination using that interface, a point-to-point tunnel interface will go into a down state.
Router> enableRouter# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# interface tunnel 0Router(config-if)# tunnel route-via ethernet0 preferredRouter(config-if)# endRouter# show running-config interface tunnel 0Building configuration...Current configuration : 147 bytes!interface Tunnel0ip unnumbered Loopback0tunnel source Loopback0tunnel destination 10.73.0.102tunnel route-via Ethernet0 preferredendAdditional References
Related Documents
Implementing tunnels
Cisco IOS Interface and Hardware Component Configuration Guide
Interface and hardware component commands: tunnel route-via, show interfaces tunnel
Cisco IOS Interface and Hardware Component Command Reference
Debug command: debug tunnel route-via
Standards
MIBs
None
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
Technical Assistance
Feature Information for Tunnel Route Selection
Table 1 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
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.
Note
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at 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. (1005R)
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.
© 2006-2009 Cisco Systems, Inc. All rights reserved.
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