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The MPLS Traffic Engineering (TE)--IP Explicit Address Exclusion feature provides a means to exclude a link or node from the path for a Multiprotocol Label Switching (MPLS) TE label switched path (LSP).
The feature is enabled through the ip explicit-path command that allows you to create an IP explicit path and enter a configuration submode for specifying the path. The feature adds to the submode commands the exclude-address command for specifying addresses to exclude from the path.
If the excluded address for an MPLS TE LSP identifies a flooded link, the constraint-based shortest path first (CSPF) routing algorithm does not consider that link when computing paths for the LSP. If the excluded address specifies a flooded MPLS TE router ID, the CSPF routing algorithm does not allow paths for the LSP to traverse the node identified by the router ID.
Your network must support the following Cisco IOS XE features in order to support IP explicit address exclusion:
MPLS
IP Cisco Express Forwarding
Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF)
MPLS TE will accept an IP explicit path comprised of either all excluded addresses configured by the exclude-address command or all included addresses configured by the next-address command, but not a combination of both.
MPLS is an Internet Engineering Task Force (IETF)-specified framework that provides for the efficient designation, routing, forwarding, and switching of traffic flows through the network.MPLS is a method that forwards IP traffic using a label. This label instructs the routers and the switches in the network where to forward the packets based on preestablished IP routing information.
Traffic engineering (TE) is the process of adjusting bandwidth allocations to ensure that enough is left for high-priority traffic.
In MPLS TE, the upstream router creates a network tunnel for a particular traffic stream, then fixes the bandwidth available for that tunnel.
Cisco Express Forwarding is an advanced, Layer 3 switching technology inside a router. It defines the fastest method by which a Cisco router forwards packets from ingress to egress interfaces. The ip cef command enables Cisco Express Forwarding globally, and the ip route-cache cef command enables Cisco Express Forwarding on an interface.
| Command or Action | Purpose | |
|---|---|---|
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Step 1 |
enable Example: |
Enables privileged EXEC mode.
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Step 2 |
configure terminal Example: |
Enters global configuration mode. |
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Step 3 |
ip explicit-path {name path-name | identifier number } [enable | disable ] Example: |
Specifies the name or number of the explicit path, and enables the path, and enters explicit-path configuration mode. |
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Step 4 |
exclude-address ip-address Example: |
Excludes the specified link or node from consideration by the constraint-based SPF.
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Step 5 |
exit Example: |
Exits from explicit-path configuration mode, and returns to global configuration mode. |
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Step 6 |
exit Example: |
Exits from global configuration mode, and returns to privileged EXEC mode. |
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Step 7 |
show ip explicit-path Example: |
Displays information about configured IP explicit paths. |
| Command or Action | Purpose | |||
|---|---|---|---|---|
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Step 1 |
enable Example: |
Enables privileged EXEC mode.
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Step 2 |
configure terminal Example: |
Enters global configuration mode. |
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Step 3 |
interface tunnel number Example: |
Configures an interface type and enters interface configuration mode. |
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Step 4 |
ip unnumbered loopback0 Example: |
Assigns the tunnel interface an IP address.
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Step 5 |
tunnel destination ip-address Example: |
Specifies the destination for a tunnel.
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Step 6 |
tunnel mode mpls traffic-eng Example: |
Sets the tunnel encapsulation mode to MPLS traffic engineering. |
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Step 7 |
tunnel mpls traffic-eng bandwidth bandwidth Example: |
Configures the bandwidth for the MPLS traffic engineering tunnel. |
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Step 8 |
tunnel mpls traffic-eng path-option number {dynamic | explicit {name path-name | ID path-number }} [lockdown ] Example: |
Configures the tunnel to use a named IP explicit path or a path dynamically calculated from the traffic engineering topology database.
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Step 9 |
exit Example: |
Exits from interface configuration mode. |
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Step 10 |
exit Example: |
Exits to privileged EXEC mode. |
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Step 11 |
show mpls traffic eng tunnels Example: |
Shows information about tunnels, including the current tunnel path if a tunnel is operational.
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The following example shows how to configure an MPLS TE tunnel with two path options: a preferred explicit path with an excluded address and a backup dynamic path.
Configure the IP explicit path named OmitR12, which excludes the router with router ID 10.12.12.12:
ip explicit-path name OmitR12
exclude-address 10.12.12.12
Explicit Path name OmitR12:
1: exclude-address 10.12.12.12
exit To verify the configuration of the explicit path, use the show ip explicit-path command.
show ip explicit-paths name OmitR12
PATH OmitR12 (loose source route, path complete, generation 3)
1: exclude-address 10.12.12.12 Note |
You must know the router IDs for LSRs (nodes) in the network; in this example, that 10.12.12.12 is a router ID. Otherwise, it will not be apparent whether the specified address is the IP address of a link or a router ID. |
The following example configures Tunnel11 with its two options, where the preferred path option is the IP explicit path OmitR2:
interface tunnel11
ip unnumbered loopback0
tunnel destination 10.11.11.11
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng path-option 1 explicit name OmitR12
tunnel mpls traffic-eng path-option 2 dynamicNote |
There are additional commands for configuring properties for TE tunnels such as bandwidth and priority. For descriptions of those commands, refer to the Cisco IOS Multiprotocol Label Switching Command Reference. |
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Related Topic |
Document Title |
|---|---|
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MPLS commands |
Cisco IOS Multiprotocol Label Switching Command Reference |
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MPLS configuration information |
Cisco IOS XE Multiprotocol Label Switching Configuration Guide |
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Standard |
Title |
|---|---|
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
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MIB |
MIBs Link |
|---|---|
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No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
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RFC |
Title |
|---|---|
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No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
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Description |
Link |
|---|---|
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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. |
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.|
Feature Name |
Releases |
Feature Configuration Information |
|---|---|---|
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MPLS Traffic Engineering (TE)--IP Explicit Address Exclusion |
Cisco IOS XE Release 2.3 |
The MPLS Traffic Engineering (TE)--IP Explicit Address Exclusion feature provides a means to exclude a link or node from the path for Multiprotocol Label Switching (MPLS) TE label switched path (LSP). This feature was integrated into Cisco IOS XE Release 2.3. The following command was introduced by this feature: exclude-address . |
Cisco Express Forwarding --A means for accelerating the forwarding of packets within a router, by storing route lookup information in several data structures instead of in a route cache.
IP explicit path --A list of IP addresses, each representing a node or link in the explicit path.
link --Network communications channel consisting of a circuit or transmission path and all related equipment between a sender and a receiver. Sometimes referred to as a line or a transmission link.
MPLS --Multiprotocol Label Switching. Switching method that forwards IP traffic using a label. This label instructs the routers and the switches in the network where to forward the packets based on preestablished IP routing information.
node --Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be interconnected by links, and serve as control points in the network.
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