To enable the distribution of labels associated with the IP default route, use the mpls ip default-route command in global configuration mode.

Syntax Description

This command has no arguments or keywords.

Command Default

No distribution of labels for the IP default route.

Command Modes

Global configuration

Command History

Usage Guidelines

Dynamic label switching (that is, distribution of labels based on routing protocols) must be enabled before you can use the mpls ip default-route command.

Related Commands

To enable Multiprotocol Label Switching (MPLS) forwarding of IPv4 and IPv6 packets along normally routed paths for the platform, use the mpls ip command in global configuration mode. To disable this feature, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Label switching of IPv4 and IPv6 packets along normally routed paths is enabled for the platform.

Command Modes

Global configuration

Command History

Usage Guidelines

MPLS forwarding of IPv4 and IPv6 packets along normally routed paths (sometimes called dynamic label switching) is enabled by this command. For a given interface to perform dynamic label switching, this switching function must be enabled for the interface and for the platform.

The no form of this command stops dynamic label switching for all platform interfaces regardless of the interface configuration; it also stops distribution of labels for dynamic label switching. However, the no form of this command does not affect the sending of labeled packets through label switch path (LSP) tunnels.

Related Commands

To enable Multiprotocol Label Switching (MPLS) forwarding of IPv4 and IPv6 packets along normally routed paths for a particular interface, use the mpls ip command in interface configuration mode. To disable this configuration, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

MPLS forwarding of IPv4 and IPv6 packets along normally routed paths for the interface is disabled.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

MPLS forwarding of IPv4 and IPv6 packets along normally routed paths is sometimes called dynamic label switching. If dynamic label switching has been enabled for the platform when this command is issued on an interface, label distribution for the interface begins with the periodic transmission of neighbor discovery Hello messages on the interface. When the outgoing label for a destination routed through the interface is known, packets for the destination are labeled with that outgoing label and forwarded through the interface.

The no form of this command causes packets routed out through the interface to be sent unlabeled; this form of the command also terminates label distribution for the interface. However, the no form of the command does not affect the sending of labeled packets through any link-state packet (LSP) tunnels that might use the interface.

To specify the Label Distribution Protocol (LDP) for a platform, use the mpls label protocol command in global configuration mode. To restore the default LDP, use the no form of this command.

Syntax Description

Command Default

LDP is the default label distribution protocol.

Command Modes

Global configuration

Command History

Usage Guidelines

If neither the global mpls label protocol ldp command nor the interface mpls label protocol ldp command is used, all label distribution sessions use LDP.

To specify the label distribution protocol for an interface, use the mpls label protocol command in interface configuration mode. To remove the label distribution protocol from the interface, use the no form of this command.

Syntax Description

Command Default

If no protocol is explicitly configured for an interface, the label distribution protocol that was configured for the platform is used. To set the platform label distribution protocol, use the global mpls label protocol command.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

To successfully establish a session for label distribution for a link connecting two label switch routers (LSRs), the link interfaces on the LSRs must be configured to use the same label distribution protocol. If there are multiple links connecting two LSRs, all of the link interfaces connecting the two LSRs must be configured to use the same protocol.

To configure the range of local labels available for use with Multiprotocol Label Switching (MPLS) applications on packet interfaces, use thempls label range command in global configuration mode. To revert to the platform defaults, use the no form of this command.

Syntax Description

Command Default

The platform’s default values are used.

Command Modes

Global configuration

Command History

Usage Guidelines

The labels 0 through 15 are reserved by the IETF (see RFC 3032, MPLS Label Stack Encoding, for details) and cannot be included in the range specified in the mpls label range command. If you enter a 0 in the command, you will get a message that indicates that the command is an unrecognized command.

The label range defined by thempls label range command is used by all MPLS applications that allocate local labels (for dynamic label switching, MPLS traffic engineering, MPLS Virtual Private Networks (VPNs), and so on).

You can use label distribution protocols, such as Label Distribution Protocol (LDP), to reserve a generic range of labels from 16 through 1048575 for dynamic assignment.

You specify the optional static keyword, to reserve labels for static assignment. The MPLS Static Labels feature requires that you configure a range of labels for static assignment. You can configure static bindings only from the current static range. If the static range is not configured or is exhausted, then you cannot configure static bindings.

The range of label values is 16 to 4096. The maximum value defaults to 4096. You can split for static label space between say 16 to 100 and for dynamic label space between 101 to 4096.

The upper and lower minimum static label values are displayed in the help line. For example, if you configure the dynamic label with a minimum value of 16 and a maximum value of 100, the help lines display as follows:

Switch(config)# mpls label range 16 100 static ?
<100>  Upper Minimum static label value
<16>         Lower Minimum static label value
Reserved Label Range  --> 0    to 15
Available Label Range --> 16   to 4096
Static Label Range    --> 16   to 100
Dynamic Label Range   --> 101  to 4096

In this example, you can configure a static range from 16 to 100.

If the lower minimum static label space is not available, the lower minimum is not displayed in the help line. For example:

Switch(config)# mpls label range 16 100 static ?
  <16-100>  static label value range

Related Commands

To display the range of local labels available for use on packet interfaces, use the show show mpls label range command in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC

Command History

Usage Guidelines

You can use the mpls label range command to configure a range for local labels that is different from the default range. The show mpls label range command displays both the label range currently in use and the label range that will be in use following the next switch reload.

Related Commands