- 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
- Finding Feature Information
- Prerequisites for Tunnel Route Selection
- Restrictions for Tunnel Route Selection
- Information About Tunnel Route Selection
- How to Configure Tunnel Route Selection
Tunnel Route Selection
The 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
- Prerequisites for Tunnel Route Selection
- Restrictions for Tunnel Route Selection
- Information About Tunnel Route Selection
- How to Configure Tunnel Route Selection
- Configuration Examples for Tunnel Route Selection
- Additional References
- Feature Information for Tunnel Route Selection
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 Table at the end of this document.
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.
Prerequisites for Tunnel Route Selection
Tunnel interfaces are configured.
Restrictions for Tunnel Route Selection
This feature is supported in the following tunnel modes only:
- Generic Routing Encapsulation (GRE) IP
- GRE Multipoint
- IP in IP
- Mobile User Datagram Protocol (UDP)
This feature is not supported on a tunnel when the tunnel transport is a GRE Multipoint tunnel.
Supported Configuration
interface tunnel 0 tunnel mode gre multipoint tunnel route-via tunnel 1 interface tunnel 1 tunnel mode gre ip
Unsupported Configuration
interface tunnel 0 tunnel mode gre multipoint tunnel route-via tunnel 1 interface tunnel 1 tunnel mode gre multipoint
Information 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.
The figure below compares default tunnel behavior with the Tunnel Route Selection behavior.
| Figure 1 | Tunnel Route Selection Traffic |
How to Configure Tunnel Route Selection
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.
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-via Tunnel route-via debugging is on Router# *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 forward Router# undebug tunnel route-via Tunnel route-via debugging is off
What 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 0 Building configuration... Current configuration : 147 bytes ! interface Tunnel0 ip unnumbered Loopback0 tunnel source Loopback0 tunnel destination 10.73.0.102 tunnel route-via Ethernet0 preferred end Router# show interfaces tunnel 0 | include route-via
Tunnel route-via feature is on [Ethernet0, preferred]
Configuration Examples for Tunnel Route Selection
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> enable Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# interface tunnel 0 Router(config-if)# tunnel route-via ethernet0 preferred Router(config-if)# end Router# show running-config interface tunnel 0 Building configuration... Current configuration : 147 bytes ! interface Tunnel0 ip unnumbered Loopback0 tunnel source Loopback0 tunnel destination 10.73.0.102 tunnel route-via Ethernet0 preferred end
Additional References
Related Documents
| Related Topic |
Document Title |
|---|---|
| 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 |
Cisco IOS Debug Command Reference |
Standards
| Standard |
Title |
|---|---|
| None |
-- |
MIBs
| MIB |
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: |
RFCs
| RFC |
Title |
|---|---|
| None |
-- |
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 Tunnel Route Selection
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 1 | Feature Information for Tunnel Route Selection |
| Feature Name |
Releases |
Feature Information |
|---|---|---|
| Tunnel Route Selection |
12.4(11)T 15.0(1)M |
The 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. The following commands were introduced or modified: debug tunnel route-via, tunnel route-via, show interfaces tunnel. |
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.
Feedback