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Open Shortest Path First (OSPF) or Intermediate System-to-Intermediate System (IS-IS)
Restrictions for MPLS Traffic
Engineering—Configurable Path Calculation Metric for Tunnels
Unless explicitly configured, the TE link metric for a given link is the IGP link metric.
When the TE link metric is used to represent a link property that is different
from cost/distance, you must configure every network link that can be used for
TE tunnels with a TE link metric that represents that property. You can do this
by using the mplstraffic-engadministrative-weight command. Failure to do so might
cause tunnels to use unexpected paths.
MPLS traffic engineering supports only a single IGP process/instance. Multiple IGP
processes/instances are not supported. MPLS traffic engineering should not be
configured in more than one IGP process/instance.
Information About MPLS Traffic Engineering—Configurable Path Calculation Metric for
Tunnels
The following section provides information about Configurable Path Calculation Metric for
MPLS Traffic Engineering tunnels.
Overview
The MPLS Traffic Engineering—Configurable Path Calculation Metric for Tunnels feature
enables you to control the metric used in path calculation for traffic engineering (TE)
tunnels on a per-tunnel basis.
When MPLS TE is configured in a network, the Interior Gateway Protocol (IGP) floods two
metrics for every link. The metrics are the normal IGP (OSPF or IS-IS) link metric and a
TE link metric. The IGP uses the IGP link metric in the normal way to compute routes for
destination networks.
You can specify that the path calculation for a given tunnel is based on either of the
following:
IGP link metrics
TE link metrics, which you can configure so that they represent the needs of a
particular application. For example, the TE link metrics can be configured to
represent link transmission delay.
Benefits
When Traffic Engineering (TE) tunnels carry two types of traffic, the Configurable Path
Calculation Metric for Tunnels feature allows you to tailor tunnel path selection to the
requirements of each type of traffic.
For example, suppose that certain tunnels are to carry voice traffic (which requires low
delay) and other tunnels are to carry data. In this situation, you can use the TE link
metric to represent link delay and do the following:
Configure tunnels that carry voice to use the TE link metric set to represent
link delay for path calculation.
Configure tunnels that carry data to use the IGP metric for path
calculation.
How to Configure MPLS Traffic Engineering—Configurable Path Calculation Metric for
Tunnels
The following section provides information about the configuration steps for
Configurable Path Calculation Metric for Tunnels for MPLS Traffic Engineering.
Configuring a Platform to Support Traffic
Engineering Tunnels
To configure a platform to support Traffic Engineering tunnels, perform this procedure.
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode. Enter your password, if prompted.
Enables the MPLS traffic engineering tunnel feature on a device.
Step 5
exit
Example:
Device(config)# exit
Exits global configuration mode and returns to privileged EXEC mode.
Configuring IS-IS for MPLS Traffic
Engineering
Note
MPLS traffic engineering supports only a single IGP process or
instance. Multiple IGP processes or instances are not
supported. MPLS traffic engineering should not be configured
in more than one IGP process or instance.
To configure IS-IS for MPLS traffic engineering, perform the following
steps.
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode. Enter your password, if
prompted.
Step 2
configure terminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
router isis
Example:
Device(config)# router isis
Enables IS-IS routing and specifies an IS-IS process.
The device enters configuration mode.
Step 4
mpls traffic-eng
level
Example:
Device(config-router)# mpls traffic-eng level-1
Turns on MPLS traffic engineering for IS-IS level 1.
Step 5
mpls traffic-eng
level
Example:
Device(config-router)# mpls traffic-eng level-2
Turns on MPLS traffic engineering for IS-IS level 2.
Configures an interface type and enters interface configuration mode.
The type argument is the type of interface to be
configured.
The slot argument is the chassis slot number.
The/subslot keyword and argument pair is the secondary slot
number. The slash (/) is required.
The/port keyword and argument pair is the port or interface
number. The slash (/) is required.
The .subinterface-numberkeyword and argument pair is the
subinterface number in the range 1–4294967293. The number that precedes the period
(.) must match the number to which this subinterface belongs.
Overrides the IGP administrative weight (cost) of the link.
The weight argument is the cost of the link.
Step 5
exit
Example:
Device(config-if)# exit
Exits interface configuration mode and returns to global configuration mode.
Step 6
exit
Example:
Device(config)# exit
Exits global configuration mode and returns to privileged EXEC mode.
Configuring an MPLS Traffic Engineering
Tunnel
To configure a preferred explicit path for an MPLS TE tunnel, perform this procedure.
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode. Enter your password, if prompted.
Step 2
configureterminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
interfacetunnelnumber
Example:
Device(config)# interface Tunnel0
Configures an interface type and enters interface configuration mode.
The number argument is the number of the tunnel.
Step 4
ipunnumberedtypenumber
Example:
Device(config-if)# ip unnumbered loopback0
Enables IP processing on an interface without assigning an explicit IP address to the
interface.
The type and number arguments
name the type and number of another interface on which the router has an assigned IP
address. It cannot be another unnumbered interface.
An MPLS traffic engineering tunnel interface should be unnumbered because it
represents a unidirectional link.
Step 5
tunneldestinationip-address
Example:
Device(config-if)# tunnel destination 192.168.4.4
Specifies the destination for a tunnel interface.
Theip-address argument must be the MPLS traffic engineering router
ID of the destination device.
Step 6
tunnelmodemplstraffic-eng
Example:
Device(config-if)# tunnel mode mpls traffic-eng
Sets the tunnel encapsulation mode to MPLS traffic engineering.
Configures the bandwidth for the MPLS traffic engineering tunnel.
The bandwidth argument is a number in kilobits per
second that is set aside for the MPLS traffic engineering tunnel. Range is from 1
through 4294967295.
Note
If automatic bandwidth is configured for the tunnel, use the
tunnelmplstraffic-engbandwidth command to configure the initial tunnel bandwidth.
Configures the tunnel to use a named IP explicit path or a path dynamically calculated
from the traffic engineering topology database.
The number argument is the preference for this path
option. When you configure multiple path options, lower numbered options are
preferred. Valid values are from 1 through 1000.
The dynamic keyword indicates that the path of the LSP
is dynamically calculated.
The explicit keyword indicates that the path of the LSP
is an IP explicit path.
The namepath-name keyword and argument are the path name of the IP
explicit path that the tunnel uses with this option.
The identifierpath-number keyword and argument pair names the path
number of the IP explicit path that the tunnel uses with this option. The range is
from 1 through 65535.
The lockdown keyword specifies that the LSP cannot be
reoptimized.
Note
A dynamic path is used if an explicit path is currently unavailable.
Step 9
exit
Example:
Device(config-if)# exit
Exits interface configuration mode and returns to global configuration mode.
Configuring the Metric Type for Tunnel Path
Calculation
Unless explicitly configured, the traffic engineering link metric type is used for tunnel
path calculation. You can use two commands to control the metric type to use: an interface
configuration command that specifies the metric type to be used for a particular TE tunnel.
And a global configuration command that specifies the metric type to use for TE tunnels for
which a metric type is unspecified by the interface configuration command.
Note
If you do not enter either of the path selection metrics commands, the traffic
engineering (TE) metric is used.
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode. Enter your password, if prompted.
Step 2
configureterminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
interfacetunnelnumber
Example:
Device(config)# interface Tunnel0
Configures an interface type and enters interface configuration mode.
Specifies the metric type to use when a metric type was not explicitly configured for
a given tunnel.
The igp keyword specifies the use of the Interior
Gateway Protocol (IGP) metric.
The te keyword specifies the use of the traffic
engineering (TE) metric. This is the default.
Step 7
exit
Example:
Device(config)# exit
Exits global configuration mode and returns to privileged EXEC mode.
Verifying the Tunnel Path Metric Configuration
To verify the tunnel path metric configuration, perform the following procedure.
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode. Enter your password, if prompted.
Step 2
showmplstraffic-engtopology
Example:
Device# show mpls traffic-eng topology
Displays TE and IGP metrics for each link. You can verify that link metrics
are correctly configured for a network.
Step 3
showmplstraffic-engtunnels
Example:
Device# show mpls traffic-eng tunnels
Displays the link metric used for tunnel path calculation. You can verify
that the desired link metrics are used for each tunnel.
Step 4
exit
Example:
Device# exit
Returns to user EXEC mode.
Configuration Examples for MPLS Traffic
Engineering—Configurable Path Calculation Metric for Tunnels
The following section provides configuration examples for configuring a path
calculation metric for tunnels.
Example: Configuring Link Type and Metrics
for Tunnel Path Selection
The section illustrates how to configure the link metric type to use for tunnel path
selection. And how to configure the link metrics themselves. The configuration
commands included focus on specifying the metric type for path calculation and
assigning metrics to links. You will need additional commands are required to fully
configure the example scenario. For example, the IGP commands for traffic
engineering and the link interface commands for enabling traffic engineering and
specifying available bandwidth.
The examples in this section support the simple network technology shown in the following
figure.
In the figure above:
Tunnel1 and Tunnel2 run from S1 (headend) to S4 (tailend).
Tunnel3 runs from S1 to S5.
Path calculation for Tunnel1 and Tunnel3 should use a metric that represents
link delay because these tunnels carry voice traffic.
Path calculation for Tunnel2 should use IGP metrics because MPLS TE carries
data traffic with no delay requirement.
Configuration fragments follow for each of the devices that illustrate the configuration
relating to link metrics and their use in tunnel path calculation. TE metrics that
represent link delay must be configured for the network links on each of the
devices. And the three tunnels must be configured on S1.
This configuration fragments force Tunnel1 to take path S1-S3-S4, Tunnel2 to take path
S1-S2-S4, and Tunnel3 to take path S1-S3-S4-S5 (assuming the links have sufficient
bandwidth to accommodate the tunnels).
S1Configuration
The following example shows how to configure the tunnel headend S1 for Tunnel1, Tunnel2, and
Tunnel3 in the preceding figure:
The following example shows how to configure S2 in the preceding figure:
interface port channel 10
mpls traffic-eng administrative-weight 15 !TE metric different from IGP metric
interface port channle 20
mpls traffic-eng administrative-weight 40 !TE metric different from IGP metric
S3Configuration
The following example shows how to configure S3 in the preceding figure:
interface port channel 40
mpls traffic-eng administrative-weight 15 !TE metric different from IGP metric
interface port channel 50
mpls traffic-eng administrative-weight 15 !TE metric different from IGP metric
interface port channel 30
mpls traffic-eng administrative-weight 5 !TE metric different from IGP metric
S4Configuration
The following example shows how to configure R4 in the preceding figure:
interface port channel 20
mpls traffic-eng administrative-weight 15 !TE metric different from IGP metric
interface port channel 30
mpls traffic-eng administrative-weight 15 !TE metric different from IGP metric
interface port channel 60
mpls traffic-eng administrative-weight 5 !TE metric different from IGP metric
S5Configuration
The following example shows how to configure S5 in the preceding figure:
interface port channel 50
mpls traffic-eng administrative-weight 15 !TE metric different from IGP metric
interface port channel 60
mpls traffic-eng administrative-weight 5 !TE metric different from IGP metric
Example: Verifying the Tunnel Path Metric Configuration
The following examples show how to verify the Tunnel Path Metric configuration.
The following example is a sample output of the show mpls traffic-eng
topology command. This command displays the TE and IGP metrics for
each link.
The following example is a sample output of the showmplstraffic-engtunnels command. This command displays the link metric used
for tunnel path calculation.
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Feature History for MPLS Traffic
Engineering—Configurable Path Calculation Metric for Tunnels
This table provides release and related information for the features explained in
this module.
These features are available in all the releases subsequent to the one they were
introduced in, unless noted otherwise.
Release
Feature
Feature Information
Cisco IOS XE Bengaluru 17.6.1
MPLS Traffic Engineering—Configurable Path Calculation Metric
for Tunnels
The MPLS Traffic Engineering—Configurable Path Calculation Metric for Tunnels feature
enables you to control the metric used in path calculation for
traffic engineering (TE) tunnels on a per-tunnel basis.
Use the Cisco Feature Navigator to find information about platform and software image
support. To access Cisco Feature Navigator, go to https://cfnng.cisco.com/