In which configuration mode is mpls traffic-eng used?

The mpls traffic-eng command is entered in Global Config mode on Cisco IOS-XR devices.

mplsGlobal Config

mpls traffic-eng

Enables MPLS Traffic Engineering (MPLS-TE) and enters MPLS-TE configuration submode on Cisco IOS-XR.

Definition: mpls traffic-eng is a Cisco IOS-XR global config command. Enables MPLS Traffic Engineering (MPLS-TE) and enters MPLS-TE configuration submode on Cisco IOS-XR.

Overview

The 'mpls traffic-eng' command is the gateway to configuring MPLS Traffic Engineering (MPLS-TE) on Cisco IOS-XR. MPLS-TE is a technology that allows network operators to control the path that traffic takes through an MPLS network, optimizing bandwidth utilization and meeting service-level agreements. By entering this command, the user enters a configuration submode where global TE parameters can be set.

This includes defining reoptimization timers, path selection preferences, and signaling protocols (RSVP-TE). On IOS-XR, MPLS-TE is tightly integrated with the underlying IGP (OSPF or ISIS) to distribute link attributes such as bandwidth, delay, and administrative groups. The command does not directly enable TE on interfaces; that requires separate interface-level configuration.

MPLS-TE is essential for deploying traffic-engineered LSPs (TE tunnels) that can be used for bandwidth guarantees, fast reroute, and load balancing. In troubleshooting workflows, the 'mpls traffic-eng' command is the starting point for verifying global TE settings before diving into tunnel-specific issues. It is also used to configure features like auto-bandwidth, path protection, and logging of TE events.

Understanding this command is fundamental for any network engineer working with MPLS-TE on IOS-XR platforms.

Syntax·Global Config

mpls traffic-eng

When to Use This Command

Configuring MPLS-TE tunnels for traffic engineering across a service provider backbone.
Setting up bandwidth reservations and explicit paths for latency-sensitive traffic.
Enabling fast reroute (FRR) protection for MPLS-TE tunnels.
Integrating MPLS-TE with ISIS or OSPF for link-state distribution of TE attributes.

Parameters

Parameter	Syntax	Required	Description
mpls traffic-eng	mpls traffic-eng	Required	This command has no parameters. It simply enters the MPLS-TE configuration submode. All subsequent TE-related global commands are issued under this submode.

Command Examples

Enter MPLS-TE Configuration Mode

mpls traffic-eng

RP/0/RP0/CPU0:router(config)# mpls traffic-eng
RP/0/RP0/CPU0:router(config-mpls-te)#

The prompt changes to (config-mpls-te)# indicating MPLS-TE configuration mode is active.

Configure MPLS-TE with ISIS

mpls traffic-eng
router isis 1
mpls traffic-eng level-2-only
mpls traffic-eng router-id Loopback0

RP/0/RP0/CPU0:router(config)# mpls traffic-eng
RP/0/RP0/CPU0:router(config-mpls-te)# exit
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis)# mpls traffic-eng level-2-only
RP/0/RP0/CPU0:router(config-isis)# mpls traffic-eng router-id Loopback0

After entering MPLS-TE mode, the user exits and configures ISIS to distribute TE information. 'level-2-only' restricts TE to Level-2 only. 'router-id' sets the stable router ID for TE.

Understanding the Output

The command 'mpls traffic-eng' itself does not produce output; it changes the CLI prompt to indicate the user is in MPLS-TE configuration submode. The prompt changes from 'config' to 'config-mpls-te'. This submode allows configuration of global MPLS-TE parameters such as reoptimization timers, path selection, and signaling.

To verify MPLS-TE configuration, use 'show mpls traffic-eng' commands. For example, 'show mpls traffic-eng tunnels' displays tunnel status, bandwidth, and path information. Key fields include: Tunnel Name, Status (up/down), LSP ID, Source/Destination, Bandwidth, and Path.

Healthy values show 'up' status and bandwidth reservations matching configured values. Problem values include 'down' status, 'bandwidth not available', or path errors.

Configuration Scenarios

Basic MPLS-TE Configuration with ISIS

Service provider network using ISIS as IGP, need to enable MPLS-TE for tunnel deployment.

Topology

R1 --- R2 --- R3
Loopback0: 1.1.1.1, 2.2.2.2, 3.3.3.3

Steps

1.Enter global configuration mode.
2.Enter MPLS-TE submode with 'mpls traffic-eng'.
3.Configure global TE parameters (optional).
4.Exit to global config.
5.Configure ISIS to distribute TE information.
6.Enable MPLS-TE on interfaces.

Configuration

!
mpls traffic-eng
!
router isis 1
 net 49.0001.0000.0000.0001.00
 mpls traffic-eng level-2-only
 mpls traffic-eng router-id Loopback0
!
interface GigabitEthernet0/0/0/0
 ipv4 address 10.1.1.1 255.255.255.0
 mpls traffic-eng
!
interface Loopback0
 ipv4 address 1.1.1.1 255.255.255.255
!

Verify: Use 'show mpls traffic-eng tunnels summary' to verify TE is enabled. Use 'show isis mpls traffic-eng adjacency' to verify TE link information exchange.

Watch out: The 'mpls traffic-eng' command under the interface is required; without it, the interface cannot be used for TE tunnels even if the IGP is configured.

Troubleshooting with This Command

When troubleshooting MPLS-TE on IOS-XR, the 'mpls traffic-eng' command is the first step to ensure global TE configuration is present. If TE tunnels are not coming up, verify that the router is in MPLS-TE submode by checking the prompt. Common issues include missing 'mpls traffic-eng' under interfaces, incorrect IGP configuration, or mismatched TE parameters.

Use 'show mpls traffic-eng tunnels' to check tunnel status; if tunnels are down, examine the path error using 'show mpls traffic-eng tunnels path' or 'show mpls traffic-eng link-management bandwidth'. Also, verify that RSVP is enabled (required for signaling) with 'show rsvp interface'. If the IGP is not distributing TE information, check 'show isis mpls traffic-eng adjacency' or 'show ospf mpls traffic-eng adjacency'.

The 'mpls traffic-eng' submode also contains logging commands like 'logging events' to capture TE events for debugging. In IOS-XR, the configuration is committed with 'commit', so ensure changes are applied. For persistent issues, check the 'mpls traffic-eng reoptimize timers' and 'path-selection' settings.

If tunnels are not using expected paths, verify explicit path definitions and administrative groups. The command 'show mpls traffic-eng topology' displays the TE topology database. Remember that on IOS-XR, the 'mpls traffic-eng' command is the foundation; without it, no TE configuration is possible.

CCNA Exam Tips

Remember that 'mpls traffic-eng' is a global configuration command that enters a submode; it does not enable TE on interfaces—that requires 'mpls traffic-eng' under the interface.

On IOS-XR, MPLS-TE is configured under the 'mpls traffic-eng' submode, not under 'router ospf' or 'router isis' directly; you must also enable TE under the IGP.

Know that the 'mpls traffic-eng router-id' command under the IGP is mandatory to set the TE router ID, typically a loopback interface.

Common Mistakes

Forgetting to enable MPLS-TE on interfaces with 'mpls traffic-eng' under the interface configuration; without this, TE tunnels cannot use the interface.

Not configuring the IGP (OSPF or ISIS) to distribute TE information; the IGP must have 'mpls traffic-eng' commands to advertise link attributes.

Using 'mpls traffic-eng' in global config but not entering the submode to configure parameters; the submode is required for most TE settings.

mpls traffic-eng vs mpls ldp

Both 'mpls traffic-eng' and 'mpls ldp' are global configuration commands that enter MPLS-related submodes, but they serve distinct functions: MPLS-TE focuses on traffic engineering and RSVP signaling, while LDP handles label distribution for basic MPLS forwarding. They are often considered together because many MPLS deployments use both for complementary roles.

Aspect	mpls traffic-eng	mpls ldp
Function	Enables MPLS-TE and RSVP-TE signaling	Enables LDP label distribution
Configuration submode	Enters MPLS-TE configuration submode	Enters MPLS LDP configuration submode
Primary protocol	RSVP-TE (Resource Reservation Protocol with Traffic Engineering extensions)	LDP (Label Distribution Protocol)
Typical use case	Traffic engineering tunnels, bandwidth reservation, fast reroute	Basic MPLS forwarding, L2VPN/L3VPN label distribution
Interaction with routing	Uses IGP TE extensions (IS-IS/OSPF) for path computation	Uses IGP for LDP synchronization and label distribution
Precedence in label assignment	TE tunnels override LDP paths for matched traffic	LDP assigns labels to all IGP routes by default

Use mpls traffic-eng when you need to configure advanced path control, bandwidth reservation, or fast reroute using RSVP-TE tunnels.

Use mpls ldp when you need to enable basic MPLS label distribution for MPLS forwarding and VPN services.

Platform Notes

On Cisco IOS-XR, the 'mpls traffic-eng' command behaves similarly to Cisco IOS but with important differences. In IOS-XR, the command enters a dedicated submode (config-mpls-te), whereas in classic IOS, TE parameters are often configured under the IGP or globally without a submode. IOS-XR requires explicit 'commit' to apply changes, unlike IOS where changes take effect immediately.

The interface-level 'mpls traffic-eng' command is also required on IOS-XR, similar to IOS. However, IOS-XR uses a modular architecture; TE configuration is part of the MPLS package. For equivalent commands on other platforms, Juniper uses 'protocols mpls' and 'protocols rsvp' under 'edit'.

On IOS-XR, RSVP is configured separately under 'rsvp' submode. Version differences: In IOS-XR 6.x and later, TE features like segment routing can coexist. Always check the specific version documentation.

The 'mpls traffic-eng' command is available in all IOS-XR releases that support MPLS-TE.

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