Rate and give feedback:  Feedback Received. Thank You!

Rate and give feedback: 

X

This document helped resolve my issue

Yes No

Additional Comments

800 characters remaining

May we contact you if necessary?

Name:  

E-mail: 

Enter a valid Email ID

Need product assistance? Contact Juniper Support

Submit

This site is protected by hCaptcha and its Privacy Policy and Terms of Service apply.

English  

English

Example: Enabling Wide IS-IS Metrics for Traffic Engineering

Understanding Wide IS-IS Metrics for Traffic Engineering

Normally, IS-IS metrics can have values up to 63. The total cost to a destination is the sum of the metrics on all outgoing interfaces along a particular path from the source to the destination. By default, the total path metric is limited to 1023. This metric value is insufficient for large networks and provides too little granularity for traffic engineering, especially with high-bandwidth links. A wider range of metrics is also required if route leaking is used.

IS-IS generates two type, length, and value (TLV) tuples, one for an IS-IS adjacency and the second for an IP prefix. To allow IS-IS to support traffic engineering, a second pair of TLVs has been added to IS-IS, one for IP prefixes and the second for IS-IS adjacency and traffic engineering information. With these TLVs, IS-IS metrics can have values up to 16,777,215 (2²⁴ – 1).

By default, Junos OS supports the sending and receiving of wide metrics. Junos OS allows a maximum metric value of 63 and generates both pairs of TLVs. To configure IS-IS to generate only the new pair of TLVs and thus to allow the wider range of metric values, you must include the wide-metrics-only statement in the IS-IS configuration.

Example: Enabling Wide IS-IS Metrics for Traffic Engineering

This example shows how to allow a wide range of metric values on IS-IS interfaces.

• Requirements
• Overview
• Configuration
• Verification

Requirements

Before you begin, configure IS-IS on both routers. See Example: Configuring IS-IS for information about the sample IS-IS configuration.

Overview

Figure 1 shows the topology used in this example.

Figure 1: IS-IS Wide Metrics Topology

This example describes the steps on Device R1.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Step-by-Step Procedure

1. Configure a metric of 100 on the interface at both IS-IS levels.
   [edit protocols isis interface lt-1/2/0.1]user@R1# set level 2 metric 100user@R1# set level 1 metric 100
2. Enable wide metrics.
   [edit protocols isis]user@R1# set level 2 wide-metrics-onlyuser@R1# set level 1 wide-metrics-only

Results

From configuration mode, confirm your configuration by entering the show protocols command. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Verification

Confirm that the configuration is working properly.

Verifying That Wide Metrics Are Enabled

Purpose

Make sure that the interface has the expected metric.

Action

From operational mode, enter the show isis interface extensive command.

IS-IS interface database:
lt-1/2/0.1
  Index: 68, State: 0x6, Circuit id: 0x1, Circuit type: 3
  LSP interval: 100 ms, CSNP interval: 10 s, Loose Hello padding
  Adjacency advertisement: Advertise
  Level 1
    Adjacencies: 1, Priority: 64, Metric: 100
    Hello Interval: 9.000 s, Hold Time: 27 s
    Designated Router: tp5-R2.02 (not us)
  Level 2
    Adjacencies: 1, Priority: 64, Metric: 100
    Hello Interval: 9.000 s, Hold Time: 27 s
    Designated Router: tp5-R2.02 (not us)

Meaning

The output shows that the metric is set to 100, as expected, at both Level 1 and Level 2.