Supported Platforms
Related Documentation
- J, M, MX, PTX, SRX, T Series
- Example: Connecting a Logical System to a Physical Router
- Example: Creating an Interface on a Logical System
Example: Connecting Logical Systems Within the Same Router Using Logical Tunnel Interfaces
This example shows how to configure logical tunnel interfaces to connect two logical systems that are configured in a single router.
Requirements
On M Series and T Series routers, you can create a logical tunnel interface if you have a Tunnel Services PIC installed on an Enhanced FPC in your routing platform.
On M40e routers, you can create a logical tunnel interface if you have a Tunnel Services PIC. (An Enhanced FPC is not required.)
On an M7i router, logical tunnel interfaces can be created by using the integrated Adaptive Services Module.
On an MX Series router, the master administrator can configure logical tunnel interfaces by including the tunnel-services statement at the [edit chassis fpc slot-number pic number] hierarchy level.
Overview
To connect two logical systems, you configure a logical tunnel interface on both logical systems. Then you configure a peer relationship between the logical tunnel interfaces, thus creating a point-to-point connection. Logical tunnel interfaces behave like regular interfaces. You can configure them with Ethernet, Frame Relay, or another encapsulation type. You can also configure routing protocols across them. In effect, the logical tunnel (lt) interfaces connect two logical systems within the same router. The two logical systems do not share routing tables. This means that you can run dynamic routing protocols between different logical systems within the same router.
You must treat each interface like a point-to-point connection because you can only connect one logical tunnel interface to another at any given time. Also, you must select an interface encapsulation type, configure a corresponding protocol family, and set the logical interface unit number of the peering lt interface.
In this example, the logical tunnel interfaces are configured to behave as Ethernet interfaces with the encapsulation ethernet statement. The IS-IS Protocol is enabled on the logical tunnel interfaces with the family iso statement.
When configuring logical tunnel interfaces, note the following:
- The peering logical interfaces must have the same physical lt interface name. For example, a logical unit on lt-0/1/0 cannot peer with a logical unit on lt-0/0/10. The FPC, PIC, and port numbers must match.
- The peering logical interfaces must be derived from the same PIC or module.
- You can configure only one peer unit for each logical interface. For example, unit 0 cannot peer with both unit 1 and unit 2.
- Logical tunnels are not supported with Adaptive Services, MultiServices, or Link Services PICs, but they are supported on the Adaptive Services Module on M7i routers.
Figure 1 shows the topology used in this example.
Figure 1: Connecting Two Logical Systems

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
The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.
To connect logical system interfaces:
- Run the show interfaces terse command to verify
that the router has a logical tunnel (lt) interface.
user@host> show interfaces terse
Interface Admin Link Proto Local Remote so-0/0/0 up down so-0/0/1 up down so-0/0/2 up down so-0/0/3 up down gr-0/1/0 up up ip-0/1/0 up up lt-0/1/0 up up ...
Configure the logical tunnel interface on Logical System LS1.
[edit]user@host# set logical-systems LS1 interfaces lt-0/1/0 unit 0 description LS1->LS2 user@host# set logical-systems LS1 interfaces lt-0/1/0 unit 0 encapsulation ethernet user@host# set logical-systems LS1 interfaces lt-0/1/0 unit 0 peer-unit 1 user@host# set logical-systems LS1 interfaces lt-0/1/0 unit 0 family inet address 10.0.8.13/30 user@host# set logical-systems LS1 interfaces lt-0/1/0 unit 0 family isoConfigure the logical tunnel interface on Logical System LS2.
[edit]user@host# set logical-systems LS2 interfaces lt-0/1/0 unit 1 description LS2->LS1 user@host# set logical-systems LS2 interfaces lt-0/1/0 unit 1 encapsulation ethernet user@host# set logical-systems LS2 interfaces lt-0/1/0 unit 1 peer-unit 0 user@host# set logical-systems LS2 interfaces lt-0/1/0 unit 1 family inet address 10.0.8.14/30 user@host# set logical-systems LS2 interfaces lt-0/1/0 unit 1 family isoIf you are done configuring the device, commit the configuration.
[edit]user@host# commit
Verification
Confirm that the configuration is working properly.
Verifying That the Logical Systems Are Up
Purpose
Make sure that the interfaces are properly configured.
Action
user@host> show interfaces terse
Interface Admin Link Proto Local Remote so-0/0/0 up down so-0/0/1 up down so-0/0/2 up down so-0/0/3 up down gr-0/1/0 up up ip-0/1/0 up up lt-0/1/0 up up lt-0/1/0.0 up up inet 10.0.8.13/30 iso lt-0/1/0.1 up up inet 10.0.8.14/30 iso ...
Verifying Connectivity Between the Logical Systems
Purpose
Make sure that the network address appears as directly connected.
Action
user@host> show route logical-system all
logical-system: LS1 inet.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 10.0.8.12/30 *[Direct/0] 00:00:34 > via lt-0/1/0.0 10.0.8.13/32 *[Local/0] 00:00:34 Local via lt-0/1/0.0 ----- logical-system: LS2 inet.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 10.0.8.12/30 *[Direct/0] 00:00:34 > via lt-0/1/0.1 10.0.8.14/32 *[Local/0] 00:00:34 Local via lt-0/1/0.1 ...
Related Documentation
- J, M, MX, PTX, SRX, T Series
- Example: Connecting a Logical System to a Physical Router
- Example: Creating an Interface on a Logical System
Published: 2013-08-28
Supported Platforms
Related Documentation
- J, M, MX, PTX, SRX, T Series
- Example: Connecting a Logical System to a Physical Router
- Example: Creating an Interface on a Logical System