Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide
Configuring MPLS TE Forwarding Adjacency
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Table of Contents

Configuring MPLS TE Forwarding Adjacency

Information About MPLS TE Forwarding Adjacency

Licensing Requirements for MPLS TE Forwarding Adjacency

Prerequisites for MPLS TE Forwarding Adjacency

Guidelines and Limitations for MPLS TE Forwarding Adjacency

Default Settings for MPLS TE Forwarding Adjacency

Configuring MPLS TE Forwarding Adjacency

Verifying the MPLS TE Forwarding Adjacency Configuration

Configuration Example for MPLS TE Forwarding Adjacency

Additional References for MPLS TE Forwarding Adjacency

Related Documents

MIBs

Feature History for MPLS TE Forwarding Adjacency

Configuring MPLS TE Forwarding Adjacency

This chapter describes how to configure Multiprotocol Label Switching (MPLS) traffic engineering (TE) forwarding adjacency on Cisco NX-OS devices.

This chapter includes the following sections:

Information About MPLS TE Forwarding Adjacency

MPLS TE forwarding adjacency allows you to handle a TE label-switched path (LSP) tunnel as a link in an Interior Gateway Protocol (IGP) network that is based on the Shortest Path First (SPF) algorithm. Both Intermediate System-to-Intermediate System (IS-IS) and Open Shortest Path First (OSPF) are supported as the IGP.

A forwarding adjacency can be created between switches regardless of their location in the network. The switches can be located multiple hops from each other, as shown in Figure 1-1.

Figure 1-1 Forwarding Adjacency Topology

As a result, a TE tunnel is advertised as a link in an IGP network with the tunnel’s cost associated with it.

Switches outside of the TE domain see the TE tunnel and use it to compute the shortest path for routing traffic throughout the network.

TE tunnel interfaces are advertised in the IGP network just like any other links. Switches can then use these advertisements in their IGPs to compute the SPF even if they are not the headend of any TE tunnels.

Licensing Requirements for MPLS TE Forwarding Adjacency

 

Product
License Requirement

Cisco NX-OS

Forwarding adjacency requires an MPLS license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Prerequisites for MPLS TE Forwarding Adjacency

Forwarding adjacency has the following prerequisites:

Guidelines and Limitations for MPLS TE Forwarding Adjacency

Forwarding adjacency has the following configuration guidelines and limitations:

  • Forwarding adjacency increases the size of the IGP database by advertising a TE tunnel as a link.
  • When you enable forwarding adjacency on a TE tunnel, the link is advertised in the IGP network as a type, length, value (TLV) 22 object without any TE sub-TLV.
  • You must configure MPLS TE forwarding adjacency tunnels bidirectionally.
  • You cannot configure MPLS TE over the logical generic routing encapsulation (GRE) tunnel interface.

Note If both forwarding adjacency and autoroute announce are configured on a link, forwarding adjacency takes precedence. The autoroute configuration takes effect automatically if the forwarding adjacency configuration is removed, but not if the forwarding adjacency path fails.


Default Settings for MPLS TE Forwarding Adjacency

Table 1-1 lists the default settings for forwarding adjacency.

 

Table 1-1 Default Settings for Forwarding Adjacency

Parameters
Default

forwarding-adjacency holdtime

Defaults to 0

Configuring MPLS TE Forwarding Adjacency

You can configure a tunnel interface for an MPLS TE forwarding adjacency.


Note You must configure a forwarding adjacency on two LSP tunnels bidirectionally from A to B and B to A. Otherwise, the forwarding adjacency is advertised but not used in the IGP network.


Prerequisites

You must have the MPLS TE feature enabled (see the “Configuring MPLS TE”).

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. interface tunnel-te number

3. forwarding-adjacency [ holdtime value ]

4. isis metric metric-value { level-1 | level-2 }

5. (Optional) show interface tunnel-te number

6. (Optional) copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

switch(config)#

Enters global configuration mode.

Step 2

interface tunnel-te number

 

Example:

switch(config)# interface tunnel-te 1

Enters TE interface configuration mode.

The number argument identifies the tunnel number to be configured.

Step 3

forwarding-adjacency [ holdtime value ]

 

Example:

switch(config-if-te)# forwarding-adjacency

Advertises a TE tunnel as a link in an IGP network. The holdtime specifies the time (in milliseconds) that TE waits after the tunnel goes down before informing the IGP. This process enables the tunnel to try to find an alternate path within that time frame and if successful, the IGP is never notified that the tunnel went down (which avoids unnecessary SPF calculations).

Step 4

isis metric metric-value { level-1 | level-2 }

 
switch(config-if-te)# isis metric 2 level-1

Configures the IS-IS metric for a tunnel interface to be used as a forwarding adjacency. You should specify the isis metric command with level-1 or level-2 to be consistent with the IGP level at which you are performing TE. Otherwise, the metric has the default value of 10.

Note Use this command only if the IGP is IS-IS. If the IGP is OSPF, use the equivalent OSPF command.

Step 5

show interface tunnel-te number

 

Example:

switch(config-if-te)# show interface tunnel-te 1

(Optional) Displays information about the TE tunnel.

Step 6

copy running-config startup-config

 

Example:

switch(config-if-te)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Verifying the MPLS TE Forwarding Adjacency Configuration

To display the MPLS TE forwarding adjacency configuration, perform one of the following tasks:

 

Command
Purpose

show mpls traffic-eng forwarding-adjacency [ ip-address ]

Displays information about MPLS TE forwarding adjacency.

show isis [ process-tag ] database [ level-1 ] [ level-2 ] [ l1 ] [ l2 ] [ detail ] [ lspid ]

Displays information about IS-IS.

For detailed information about the fields in the output from these commands, see the Cisco NX-OS MPLS Command Reference .

Configuration Example for MPLS TE Forwarding Adjacency

The following example shows how to configure a TE tunnel interface with forwarding adjacency and an IS-IS metric:

configuration terminal
feature mpls traffic-engineering
interface tunnel-te 7
forwarding-adjacency
isis metric 2 level-1

Note If both the forwarding adjacency command and the autoroute announce command appear in your configuration, the forwarding adjacency command takes precedence.


In Figure 1-2, if you have no forwarding adjacencies configured for the TE tunnels between B and F, and C and F, all the traffic that A must forward to F goes through B because B is the shortest path from A to F. (The cost from A to F is 15 through B and 20 through C.)

Figure 1-2 Using Forwarding Adjacencies

If you have forwarding adjacencies configured on the TE tunnels between B and F and C and F and also on the TE tunnels between F and B, and F and C, then when A computes the SPF algorithm, A sees two equal cost paths of 11 to F. As a result, traffic across the A–B and A–C links is shared.

Additional References for MPLS TE Forwarding Adjacency

For additional information related to the Forwarding Adjacency feature, see the following sections:

Related Documents

Related Topic
Document Title

CLI commands

Cisco Nexus 7000 Series NX-OS MPLS Command Reference

MIBs

MIB
MIBs Link
  • CISCO-IETF-FRR-MIB
  • MPLS TE-STD-MIB

To locate and download Cisco 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

Feature History for MPLS TE Forwarding Adjacency

Table 1-2 lists the release history for this feature.

 

Table 1-2 Feature History for Forwarding Adjacency

Feature Name
Releases
Feature Information

MPLS TE forwarding adjacency

5.2(1)

This feature was introduced.