Example: Disabling OSPFv2 Compatibility with RFC 1583

OSPFv2 Compatibility with RFC 1583 Overview

By default, the Junos OS implementation of OSPFv2 is compatible with RFC 1583, OSPF Version 2. This means that Junos OS maintains a single best route to an autonomous system (AS) boundary router in the OSPF routing table, rather than multiple intra-AS paths, if they are available. You can now disable compatibility with RFC 1583. It is preferable to do so when the same external destination is advertised by AS boundary routers that belong to different OSPF areas. When you disable compatibility with RFC 1583, the OSPF routing table maintains the multiple intra-AS paths that are available, which the router uses to calculate AS external routes as defined in RFC 2328, OSPF Version 2. Being able to use multiple available paths to calculate an AS external route can prevent routing loops.

Example: Disabling OSPFv2 Compatibility with RFC 1583

This example shows how to disable OSPFv2 compatibility with RFC 1583 on the routing device.

• Requirements
• Overview
• Configuration
• Verification

Requirements

No special configuration beyond device initialization is required before disabling OSPFv2 compatibility with RFC 1583.

Overview

By default, the Junos OS implementation of OSPF is compatible with RFC 1583. This means that Junos OS maintains a single best route to an autonomous system (AS) boundary router in the OSPF routing table, rather than multiple intra-AS paths, if they are available. You can disable compatibility with RFC 1583. It is preferable to do so when the same external destination is advertised by AS boundary routers that belong to different OSPF areas. When you disable compatibility with RFC 1583, the OSPF routing table maintains the multiple intra-AS paths that are available, which the router uses to calculate AS external routes as defined in RFC 2328. Being able to use multiple available paths to calculate an AS external route can prevent routing loops. To minimize the potential for routing loops, configure the same RFC compatibility on all OSPF devices in an OSPF domain.

Configuration

CLI Quick Configuration

To quickly disable OSPFv2 compatibility with RFC 1583, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode. You configure this setting on all devices that are part of the OSPF domain.

Step-by-Step Procedure

1. Disable RFC 1583.
   [edit]user@host# set protocols ospf no-rfc-1583
2. If you are done configuring the device, commit the configuration.
   [edit]user@host# commit

   Note: Repeat this configuration on each routing device that participates in an OSPF routing domain.

Results

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

Verification

Confirm that the configuration is working properly.

Verifying the OSPF Routes

Purpose

Verify that the OSPF routing table maintains the intra-AS paths with the largest metric, which the router uses to calculate AS external routes.

Action

From operational mode, enter the show ospf route detail command.