Logical Systems Overview

You can partition a single physical router into multiple logical devices that perform independent routing tasks. Because logical systems perform a subset of the tasks once handled by the physical router, logical systems offer an effective way to maximize the use of a single router.

Note: In Junos OS Release 9.3 and later, the term logical system replaces logical router. All configuration statements, operational commands, show command outputs, error messages, log messages, and SNMP MIB objects that contain the string logical-router or logical-routers are changed to logical-system and logical-systems, respectively.

Logical systems perform a subset of the actions of a physical router and have their own unique routing tables, interfaces, policies, and routing instances. A set of logical systems within a single router can handle the functions previously performed by several small routers.

The following are supported on logical systems:

• BGP, IS-IS, LDP, OSPF, RIP, RIP next generation (RIPng), RSVP, static routes, various multicast protocols, and IP version 4 (IPv4) and version 6 (IPv6) are supported at the [edit logical-systems protocols] hierarchy level.
• Basic MPLS for core provider router functionality is supported at the [edit logical-systems protocols mpls] hierarchy level.
• All policy-related statements available at the [edit policy-options] hierarchy level are supported at the [edit logical-systems policy-options] hierarchy level.
• Most routing options statements available at the [edit routing-options] hierarchy level are supported at the [edit logical-systems routing-options] hierarchy level. Only the route-record statement is not supported at the [edit logical-systems routing-options] hierarchy level.
• Graceful Routing Engine switchover (GRES) is supported.
• You can assign most interface types to a logical system, including SONET/SDH interfaces, Ethernet interfaces, Asynchronous Transfer Mode (ATM) interfaces, ATM2 interfaces, Channelized Q Performance Processor (QPP) interfaces, aggregated interfaces, link services interfaces, and multilink services interfaces.
• Source class usage, destination class usage, unicast reverse path forwarding, class of service, firewall filters, class-based forwarding, and policy-based accounting work with logical systems when you configure these features on the physical router.
• Multicast protocols, such as Protocol Independent Multicast (PIM) and Distance Vector Multicast Routing Protocol (DVMRP) are supported at the [edit logical-systems logical-system-name protocols] hierarchy level. Rendezvous point (RP) and source designated router (DR) functionality for multicast protocols within a logical system is also supported.
• The Bidirectional Forwarding Protocol (BFD) is supported.

The following restrictions apply to logical systems:

• You can configure a maximum of 15 logical systems on one physical router.
• The router has only one configuration file, which contains configuration information for the physical router and all associated logical systems. Master users can access the full configuration. However, logical system users can access only the portion of the configuration related to their particular logical system.
• All configuration commits performed by a logical system user are treated as commit private. For more information on the commit private command, see the Junos System Basics Configuration Guide.
• If a logical system experiences an interruption of its routing protocol process (rpd), the core dump output is saved in a file in the following location: /var/tmp/rpd_logical-system-name.core-tarball.number.tgz. Likewise, if you issue the restart routing command in a logical system, only the routing protocol process (rpd) for the logical system is restarted.
• If you configure trace options for a logical system, the output log file is stored in the following location: /var/tmp/logical-system-name.
• The following Physical Interface Cards (PICs) are not supported with logical systems: Adaptive Services PIC, ES PIC, Monitoring Services PIC, and Monitoring Services II PIC.
• Sampling, port mirroring, IP Security (IPsec), and Generalized MPLS (GMPLS) are not supported.
• Label-switched path (LSP) ping and traceroute for autonomous system (AS) number lookup are not supported.
• If you configure multiple logical systems, you can configure a VPLS routing instance only for the first logical system configured at the [edit logical-systems logical-system-name routing-instances instance-name protocols vpls] hierarchy level.

A virtual router is not the same as a logical system. A virtual router is a type of simplified routing instance that has a single routing table. A logical system is a partition of a physical router and can contain multiple routing instances and routing tables. For example, a logical system can contain multiple virtual router routing instances.