Example: Configuring the Multicast Forwarding Cache

Requirements

Before you begin:

• Configure the router interfaces.
• Configure an interior gateway protocol. See the Junos OS Routing Protocols Library for Security Devices.
• Configure a multicast protocol. This feature works with the following multicast protocols:
  • DVMRP
  • PIM-DM
  • PIM-SM
  • PIM-SSM

Overview

• forwarding-cache—Specifies how forwarding entries are aged out and how the number of entries is controlled.
• timeout—Specifies an idle period after which entries are aged out and removed from inet.1. You can specify a timeout in the range from 1 through 720 minutes.
• threshold—Enables you to specify threshold values on the forwarding cache to suppress (suspend) entries from being added when the cache entries reach a certain maximum and begin adding entries to the cache when the number falls to another threshold value. By default, no threshold values are enabled on the routing device.

  The suppress threshold suspends the addition of new multicast forwarding cache entries. If you do not specify a suppress value, multicast forwarding cache entries are created as necessary. If you specify a suppress threshold, you can optionally specify a reuse threshold, which sets the point at which the device resumes adding new multicast forwarding cache entries. During suspension, forwarding cache entries time out. After a certain number of entries time out, the reuse threshold is reached, and new entries are added. The range for both thresholds is from 1 through 200,000. If configured, the reuse value must be less than the suppression value. If you do not specify a reuse value, the number of multicast forwarding cache entries is limited to the suppression value. A new entry is created as soon as the number of multicast forwarding cache entries falls below the suppression value.

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 the maximum size of the forwarding cache.

   [edit routing-options multicast forwarding-cache]user@host# set threshold suppress 150000

2. Configure the amount of time (in minutes) entries can remain idle before being removed.

   [edit routing-options multicast forwarding-cache]user@host# set timeout 60

3. Configure the size of the forwarding cache when suppression stops and new entries can be added.

   [edit routing-options multicast forwarding-cache]user@host# set threshold reuse 70000

Results

Confirm your configuration by entering the show routing-options command.

Verification

To verify the configuration, run the show multicast route extensive command.

Family: INET
Group: 232.0.0.1
    Source: 11.11.11.11/32
    Upstream interface: fe-0/2/0.200
    Downstream interface list:
        fe-0/2/1.210
    Downstream interface list rejected by CAC:
        fe-0/2/1.220
    Session description: Source specific multicast
    Statistics: 0 kBps, 0 pps, 0 packets
    Next-hop ID: 337
    Upstream protocol: PIM
    Route state: Active
    Forwarding state: Forwarding
    Cache lifetime/timeout: 60 minutes
Wrong incoming interface notifications: 0