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Examples: Configuring OSPF and Logical Systems

OSPF Support for Logical Systems

This topic describes the following information:

• Introduction to Logical Systems
• OSPF and Logical Systems

Introduction to Logical Systems

With Junos OS, 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 main router, logical systems offer an effective way to maximize the use of a single routing or switching platform. Logical systems have their own unique routing tables, interfaces, policies, and routing instances.

OSPF and Logical Systems

You can configure both OSPF Version 2 (OSPFv2) and OSPF Version 3 (OSPFv3) for logical systems. In the case of OSPFv3, you can also configure OSPFv3 realms for logical systems, which allows OSPFv3 to advertise address families other than unicast IPv6.

• [edit logical-systems logical-system-name protocols (ospf | ospf3)]
• [edit logical-systems logical-system-name protocols ospf3 realm (ipv4-unicast | ipv4-multicast | ipv6-multicast)]
• [edit logical-systems logical-system-name routing-instances routing-instance-name protocols (ospf | ospf3)]
• [edit logical-systems logical-system-name routing-instances routing-instance-name protocols ospf3 realm (ipv4-unicast | ipv4-multicast | ipv6-multicast)]

Example: Configuring OSPF on Logical Systems Within the Same Router

This example shows how to configure an OSPF network using multiple logical systems that are running on a single physical router. The logical systems are connected by logical tunnel interfaces.

• Requirements
• Overview
• Configuration
• Verification

Requirements

You must connect the logical systems by using logical tunnel (lt) interfaces. See Example: Connecting Logical Systems Within the Same Router Using Logical Tunnel Interfaces.

Overview

This example shows the configuration of a single OSPF area with three logical systems running on one physical router. Each logical system has its own routing table. The configuration enables the protocol on all logical system interfaces that participate in the OSPF domain and specifies the area that the interfaces are in.

Figure 1 shows the sample network.

Figure 1: OSPF on 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

1. Configure the logical tunnel interface on Logical System LS1 connecting to Logical System LS2.

   [edit]user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 2 description LS1->LS2 user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 2 encapsulation ethernet user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 2 peer-unit 1 user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 2 family inet address 10.0.0.1/30

2. Configure the logical tunnel interface on Logical System LS1 connecting to Logical System LS3.

   [edit]user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 0 description LS1->LS3 user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 0 encapsulation ethernet user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 0 peer-unit 5 user@host# set logical-systems LS1 interfaces lt-1/2/0 unit 0 family inet address 10.0.1.2/30

3. Configure the logical tunnel interface on Logical System LS2 connecting to Logical System LS1.

   [edit]user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 1 description LS2->LS1 user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 1 encapsulation ethernet user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 1 peer-unit 2 user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 1 family inet address 10.0.0.2/30

4. Configure the logical tunnel interface on Logical System LS2 connecting to Logical System LS3.

   [edit]user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 4 description LS2->LS3 user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 4 encapsulation ethernet user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 4 peer-unit 3 user@host# set logical-systems LS2 interfaces lt-1/2/0 unit 4 family inet address 10.0.2.2/30

5. Configure the logical tunnel interface on Logical System LS3 connecting to Logical System LS2.

   [edit]user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 3 description LS3->LS2 user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 3 encapsulation ethernet user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 3 peer-unit 4 user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 3 family inet address 10.0.2.1/30

6. Configure the logical tunnel interface on Logical System LS3 connecting to Logical System LS1.

   [edit]user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 5 description LS3->LS1 user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 5 encapsulation ethernet user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 5 peer-unit 0 user@host# set logical-systems LS3 interfaces lt-1/2/0 unit 5 family inet address 10.0.1.1/30

7. Configure OSPF on all the interfaces.

   [edit]user@host# set logical-systems LS1 protocols ospf area 0.0.0.0 interface lt-1/2/0.0 user@host# set logical-systems LS1 protocols ospf area 0.0.0.0 interface lt-1/2/0.2 user@host# set logical-systems LS2 protocols ospf area 0.0.0.0 interface lt-1/2/0.1 user@host# set logical-systems LS2 protocols ospf area 0.0.0.0 interface lt-1/2/0.4 user@host# set logical-systems LS3 protocols ospf area 0.0.0.0 interface lt-1/2/0.5 user@host# set logical-systems LS3 protocols ospf area 0.0.0.0 interface lt-1/2/0.3

8. If you are done configuring the device, commit the configuration.

   [edit]user@host# commit

Results

Confirm your configuration by issuing the show logical-systems command.

Verification

Confirm that the configuration is working properly.

• Verifying That the Logical Systems Are Up
• Verifying Connectivity Between the Logical Systems

Verifying That the Logical Systems Are Up

Purpose

Make sure that the interfaces are properly configured.

Action

Interface               Admin Link Proto    Local                 Remote
...
lt-1/2/0                up    up  
lt-1/2/0.0              up    up   inet     10.0.1.2/30     
lt-1/2/0.1              up    up   inet     10.0.0.2/30     
lt-1/2/0.2              up    up   inet     10.0.0.1/30     
lt-1/2/0.3              up    up   inet     10.0.2.1/30     
lt-1/2/0.4              up    up   inet     10.0.2.2/30     
lt-1/2/0.5              up    up   inet     10.0.1.1/30     
...

Verifying Connectivity Between the Logical Systems

Purpose

Make sure that the OSPF adjacencies are established by checking the OSPF neighbor tables, checking the routing tables, and pinging the logical systems.

Action

Address          Interface              State     ID               Pri  Dead
10.0.1.1         lt-1/2/0.0             Full      10.0.1.1         128    37
10.0.0.2         lt-1/2/0.2             Full      10.0.0.2         128    33

Address          Interface              State     ID               Pri  Dead
10.0.0.1         lt-1/2/0.1             Full      10.0.0.1         128    32
10.0.2.1         lt-1/2/0.4             Full      10.0.1.1         128    36

Address          Interface              State     ID               Pri  Dead
10.0.2.2         lt-1/2/0.3             Full      10.0.0.2         128    36
10.0.1.2         lt-1/2/0.5             Full      10.0.0.1         128    37

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.0.0/30        *[Direct/0] 00:28:00
                    > via lt-1/2/0.2
10.0.0.1/32        *[Local/0] 00:28:00
                      Local via lt-1/2/0.2
10.0.1.0/30        *[Direct/0] 00:28:00
                    > via lt-1/2/0.0
10.0.1.2/32        *[Local/0] 00:28:00
                      Local via lt-1/2/0.0
10.0.2.0/30        *[OSPF/10] 00:27:05, metric 2
                    > to 10.0.1.1 via lt-1/2/0.0
                      to 10.0.0.2 via lt-1/2/0.2
224.0.0.5/32       *[OSPF/10] 00:28:03, metric 1
                      MultiRecv

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.0.0/30        *[Direct/0] 00:28:31
                    > via lt-1/2/0.1
10.0.0.2/32        *[Local/0] 00:28:32
                      Local via lt-1/2/0.1
10.0.1.0/30        *[OSPF/10] 00:27:38, metric 2
                    > to 10.0.0.1 via lt-1/2/0.1
                      to 10.0.2.1 via lt-1/2/0.4
10.0.2.0/30        *[Direct/0] 00:28:32
                    > via lt-1/2/0.4
10.0.2.2/32        *[Local/0] 00:28:32
                      Local via lt-1/2/0.4
224.0.0.5/32       *[OSPF/10] 00:28:34, metric 1
                      MultiRecv

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.0.0/30        *[OSPF/10] 00:28:23, metric 2
                    > to 10.0.2.2 via lt-1/2/0.3
                      to 10.0.1.2 via lt-1/2/0.5
10.0.1.0/30        *[Direct/0] 00:29:13
                    > via lt-1/2/0.5
10.0.1.1/32        *[Local/0] 00:29:15
                      Local via lt-1/2/0.5
10.0.2.0/30        *[Direct/0] 00:29:14
                    > via lt-1/2/0.3
10.0.2.1/32        *[Local/0] 00:29:15
                      Local via lt-1/2/0.3
224.0.0.5/32       *[OSPF/10] 00:29:16, metric 1
                      MultiRecv

PING 10.0.2.1 (10.0.2.1): 56 data bytes
64 bytes from 10.0.2.1: icmp_seq=0 ttl=64 time=1.215 ms
64 bytes from 10.0.2.1: icmp_seq=1 ttl=64 time=1.150 ms
64 bytes from 10.0.2.1: icmp_seq=2 ttl=64 time=1.134 ms

PING 10.0.0.1 (10.0.0.1): 56 data bytes
64 bytes from 10.0.0.1: icmp_seq=0 ttl=64 time=1.193 ms
64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=1.114 ms
64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=1.190 ms

Example: Configuring a Conditional OSPF Default Route Policy on Logical Systems

This example shows how to configure a conditional default route on one logical system and inject the default route into OSPF area 0.

• Requirements
• Overview
• Configuration
• Verification

Requirements

• Connect the logical systems by using logical tunnel (lt) interfaces. See Example: Connecting Logical Systems Within the Same Router Using Logical Tunnel Interfaces.
• Enable OSPF on the interfaces. See Example: Configuring OSPF on Logical Systems Within the Same Router.

Overview

In this example, OSPF area 0 contains three logical systems that are configured on a single physical router. Logical System LS3 has a BGP session with an external peer, for example, an ISP.

The ISP injects a default static route into BGP, which provides the customer network with a default static route to reach external networks. Logical System LS3 exports the default route into OSPF. The route policy on Logical System LS3 is conditional such that if the connection to the external peer goes down, the default route is no longer active in the routing tables of the logical systems in area 0. This policy prevents blackholing of traffic. Blackholing occurs when packets are dropped without notification.

Figure 2 shows the sample network.

Figure 2: OSPF with a Conditional Default Route to an ISP

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 interfaces.
   [edit logical-systems LS3 interfaces]user@R3# set lt-1/2/0 unit 3 description LS3->LS2user@R3# set lt-1/2/0 unit 3 encapsulation ethernetuser@R3# set lt-1/2/0 unit 3 peer-unit 4user@R3# set lt-1/2/0 unit 3 family inet address 10.0.2.1/30user@R3# set lt-1/2/0 unit 5 description LS3->LS1user@R3# set lt-1/2/0 unit 5 encapsulation ethernetuser@R3# set lt-1/2/0 unit 5 peer-unit 0user@R3# set lt-1/2/0 unit 5 family inet address 10.0.1.1/30user@R3# set so-0/0/2 unit 0 description LS3->ISPuser@R3# set so-0/0/2 unit 0 encapsulation ethernetuser@R3# set so-0/0/2 unit 0 peer-unit 7user@R3# set so-0/0/2 unit 0 family inet address 10.0.45.2/30

2. Configure the autonomous system (AS) number.

   [edit logical-systems LS3 routing-options]user@R3# set autonomous-system 65001
3. Configure the BGP session with the ISP device.
   [edit logical-systems LS3 protocols bgp group ext]user@R3# set type externaluser@R3# set peer-as 65000user@R3# set neighbor 10.0.45.1

4. Configure OSPF.

   [edit logical-systems LS3 protocols ospf area 0.0.0.0]user@R3# set interface lt-1/2/0.5user@R3# set interface lt-1/2/0.3

5. Configure the routing policy.

   [edit logical-systems LS3 policy-options policy-statement gendefault]user@R3# set term upstreamroutes from protocol bgpuser@R3# set term upstreamroutes from as-path upstreamuser@R3# set term upstreamroutes from route-filter 0.0.0.0/0 upto /16user@R3# set term upstreamroutes then next-hop 10.0.45.1user@R3# set term upstreamroutes then accept
   user@R3# set term end then reject
   [edit logical-systems LS3 policy-options]user@R3# set as-path upstream "^65000 "

6. Configure the generated route.

   [edit logical-systems LS3 routing-options]user@R3# set generate route 0.0.0.0/0 policy gendefault

7. Apply the export policy to OSPF.

   [edit logical-systems LS3 protocols ospf]user@R3# set export gendefault

8. If you are done configuring the device, commit the configuration.

   [edit]user@R3# commit

Results

Confirm your configuration by issuing the show logical-systems LS3 command.

Verification

Confirm that the configuration is working properly.

• Verifying that the Route to the ISP Is Working
• Verifying That the Static Route Is Redistributed
• Testing the Policy Condition

Verifying that the Route to the ISP Is Working

Purpose

Make sure connectivity is established between Logical System LS3 and the ISP’s router.

Action

Logical system: LS3

PING 10.0.45.1 (10.0.45.1): 56 data bytes
64 bytes from 10.0.45.1: icmp_seq=0 ttl=64 time=1.185 ms
64 bytes from 10.0.45.1: icmp_seq=1 ttl=64 time=1.199 ms
64 bytes from 10.0.45.1: icmp_seq=2 ttl=64 time=1.186 ms

Meaning

The ping command confirms reachability.

Verifying That the Static Route Is Redistributed

Purpose

Make sure that the BGP policy is redistributing the static route into Logical System LS3’s routing table. Also make sure that the OSPF policy is redistributing the static route into the routing tables of Logical System LS1 and Logical System LS2.

Action

inet.0: 9 destinations, 10 routes (9 active, 0 holddown, 1 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[BGP/170] 00:00:25, localpref 100
                      AS path: 65000 I
                    > to 10.0.45.1 via so-0/0/2.0

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[OSPF/150] 00:03:58, metric 0, tag 0
                    > to 10.0.1.1 via lt-1/2/0.0
10.0.2.0/30        *[OSPF/10] 03:37:45, metric 2
                      to 10.0.1.1 via lt-1/2/0.0
                    > to 10.0.0.2 via lt-1/2/0.2
224.0.0.5/32       *[OSPF/10] 03:38:41, metric 1
                      MultiRecv

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[OSPF/150] 00:04:04, metric 0, tag 0
                    > to 10.0.2.1 via lt-1/2/0.4
10.0.1.0/30        *[OSPF/10] 03:37:46, metric 2
                      to 10.0.0.1 via lt-1/2/0.1
                    > to 10.0.2.1 via lt-1/2/0.4
224.0.0.5/32       *[OSPF/10] 03:38:47, metric 1
                      MultiRecv

Meaning

The routing tables contain the default 0.0.0.0/0 route. If Logical System LS1 and Logical System LS2 receive packets destined for networks not specified in their routing tables, those packets will be sent to Logical System LS3 for further processing. If Logical System LS3 receives packets destined for networks not specified in its routing table, those packets will be sent to the ISP for further processing.

Testing the Policy Condition

Purpose

Deactivate the interface to make sure that the route is removed from the routing tables if the external network becomes unreachable.

Action

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.2.0/30        *[OSPF/10] 03:41:48, metric 2
                      to 10.0.1.1 via lt-1/2/0.0
                    > to 10.0.0.2 via lt-1/2/0.2
224.0.0.5/32       *[OSPF/10] 03:42:44, metric 1
                      MultiRecv

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.1.0/30        *[OSPF/10] 03:42:10, metric 2
                      to 10.0.0.1 via lt-1/2/0.1
                    > to 10.0.2.1 via lt-1/2/0.4
224.0.0.5/32       *[OSPF/10] 03:43:11, metric 1
                      MultiRecv

Meaning

The routing tables on Logical System LS1 and Logical System LS2 do not contain the default 0.0.0.0/0. This verifies that the default route is no longer present in the OSPF domain. To reactivate the so-0/0/2.0 interface, issue the activate logical-systems LS3 interfaces so-0/0/2 unit 0 family inet address 10.0.45.2/30 configuration-mode command.

Example: Configuring an OSPF Default Route Policy on Logical Systems

This example shows how to configure a default route on one logical system and inject the default route into OSPF area 0. In this example, OSPF area 0 contains three logical systems that are configured on a single physical router.

• Requirements
• Overview
• Configuration
• Verification

Requirements

• Connect the logical systems by using logical tunnel (lt) interfaces. See Example: Connecting Logical Systems Within the Same Router Using Logical Tunnel Interfaces.
• Enable OSPF on the interfaces. See Example: Configuring OSPF on Logical Systems Within the Same Router.

Overview

This example shows a logical system redistributing a default route to other logical systems. All logical systems are running OSPF. A common reason for a default route is to provide a path for sending traffic destined outside the OSPF domain.

In this example, the default route is not used for forwarding traffic. The no-install statement prevents the route from being installed in the forwarding table of Logical System LS3. If you configure a route so it is not installed in the forwarding table, the route is still eligible to be exported from the routing table to other protocols. The discard statement silently drops packets without notice.

Figure 3 shows the sample network.

Figure 3: OSPF with a Default Route to an ISP

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. Change the context to Logical System LS3.

   [edit]user@host> set cli logical-system LS3

2. Configure the default route on Logical System LS3.

   [edit]user@host:LS3# set routing-options static route 0.0.0.0/0 discard user@host:LS3# set routing-options static route 0.0.0.0/0 no-install

3. Configure the policy on Logical System LS3.

   [edit]user@host:LS3# set policy-options policy-statement ospf-default from protocol static user@host:LS3# set policy-options policy-statement ospf-default from route-filter 0.0.0.0/0 exact user@host:LS3# set policy-options policy-statement ospf-default then accept

4. Apply the export policy to OSPF on Logical System LS3.

   [edit]user@host:LS3# set protocols ospf export ospf-default

5. If you are done configuring the device, commit the configuration.

   [edit]user@host:LS3# commit

Results

Confirm your configuration by issuing the show logical-systems LS3 command.

Verification

Confirm that the configuration is working properly.

Verifying That the Static Route Is Redistributed

Purpose

Make sure that the OSPF policy is working by checking the routing tables.

Action

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[Static/5] 01:04:38
                      Discard
10.0.0.0/30        *[OSPF/10] 11:53:55, metric 2
                      to 10.0.2.2 via lt-1/2/0.3
                    > to 10.0.1.2 via lt-1/2/0.5
10.0.1.0/30        *[Direct/0] 11:54:50
                    > via lt-1/2/0.5
10.0.1.1/32        *[Local/0] 11:54:54
                      Local via lt-1/2/0.5
10.0.2.0/30        *[Direct/0] 11:54:50
                    > via lt-1/2/0.3
10.0.2.1/32        *[Local/0] 11:54:54
                      Local via lt-1/2/0.3
224.0.0.5/32       *[OSPF/10] 11:56:55, metric 1
                      MultiRecv

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[OSPF/150] 01:02:34, metric 0, tag 0
                    > to 10.0.1.1 via lt-1/2/0.0
10.0.0.0/30        *[Direct/0] 11:52:46
                    > via lt-1/2/0.2
10.0.0.1/32        *[Local/0] 11:52:50
                      Local via lt-1/2/0.2
10.0.1.0/30        *[Direct/0] 11:52:46
                    > via lt-1/2/0.0
10.0.1.2/32        *[Local/0] 11:52:50
                      Local via lt-1/2/0.0
10.0.2.0/30        *[OSPF/10] 11:51:56, metric 2
                    > to 10.0.1.1 via lt-1/2/0.0
                      to 10.0.0.2 via lt-1/2/0.2
224.0.0.5/32       *[OSPF/10] 11:54:50, metric 1
                      MultiRecv

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[OSPF/150] 01:05:20, metric 0, tag 0
                    > to 10.0.2.1 via lt-1/2/0.4
10.0.0.0/30        *[Direct/0] 11:55:32
                    > via lt-1/2/0.1
10.0.0.2/32        *[Local/0] 11:55:36
                      Local via lt-1/2/0.1
10.0.1.0/30        *[OSPF/10] 11:54:37, metric 2
                    > to 10.0.0.1 via lt-1/2/0.1
                      to 10.0.2.1 via lt-1/2/0.4
10.0.2.0/30        *[Direct/0] 11:55:32
                    > via lt-1/2/0.4
10.0.2.2/32        *[Local/0] 11:55:36
                      Local via lt-1/2/0.4
224.0.0.5/32       *[OSPF/10] 11:57:36, metric 1
                      MultiRecv

Meaning

The routing table on Logical System LS3 contains the default 0.0.0.0/0 route from protocol Static. The routing tables on Logical System LS1 and Logical System LS2 contain the default 0.0.0.0/0 route from protocol OSPF. If Logical System LS1 and Logical System LS2 receive packets destined for networks not specified in their routing tables, those packets will be sent to Logical System LS3 for further processing. This configuration assumes that Logical System LS3 has a connection to an ISP or another external network.

Example: Configuring an OSPF Import Policy on Logical Systems

This example shows how to configure an OSPF import policy on logical systems. OSPF import policies apply to external routes only. An external route is a route that is outside the OSPF AS.

• Requirements
• Overview
• Configuration
• Verification

Requirements

This example shows logical systems that are configured within a single physical router. The logical systems connect to each other by using logical tunnel (lt) interfaces. See Example: Connecting Logical Systems Within the Same Router Using Logical Tunnel Interfaces. Alternatively, you can use multiple physical routers.

Overview

External routes are learned by Autonomous System Border Routers (ASBRs). External routes can be advertised throughout the OSPF domain if you configure the ASBR to redistribute the route into OSPF. An external route might be learned by the ASBR from a routing protocol other than OSPF, or the external route might be a static route that you configure on the ASBR.

OSPF import policy allows you to prevent external routes from being added to the routing tables of OSPF neighbors. The import policy does not impact the OSPF database. This means that the import policy has no impact on the link-state advertisements.

OSPF import policies have practical applications. Suppose, for example, that you are using OSPF to advertise a static route to the devices in your datacenter because you want some of the devices in the datacenter to use the static route. However, you want other devices in the datacenter to ignore the static route. So, you apply the OSPF import policy on the devices that you want to ignore the static route. The filtering is done only on external routes in OSPF. The intra-area and inter-area routes are not considered for filtering. The default action is to accept the route when the route does not match the policy.

Figure 4 shows the sample network.

Figure 4: OSPF Import Policy on Logical Systems

1. LS3—Logical System LS3 has a static route to the 10.0.16.0/30 network. The next hop for the static route is 10.0.60.1. LS3 has an OSPF export policy configured. The export policy redistributes static routes from LS3’s routing table into LS3’s OSPF database. Because the static route is in LS3’s OSPF database, the route is advertised in a link state advertisement (LSA) to LS3’s OSPF neighbor. LS3’s OSPF neighbor is Logical System LS2.
2. LS2—Logical System LS2 receives the route advertisement from LS3. LS2 then installs the route into LS2’s OSPF database. LS2 has an OSPF import policy configured that matches the static route to the 10.0.16.0/30 network and prevents the static route from being installed in LS2’s routing table. However, because the route is in LS2’s OSPF database, LS2 advertises the route to its OSPF neighbor, Logical System LS1.
3. LS1—Logical System LS1 receives the route advertisement from LS2. LS1 then installs the route into LS1’s OSPF database. LS1 does not have an OSPF import policy configured that matches the static route to the 10.0.16.0/30 network . Therefore, the route gets installed in LS1’s routing table.

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 interfaces.

   [edit]user@R1# set logical-systems LS3 interfaces so-0/0/0 unit 0 family inet address 10.0.60.2/30 user@R1# set logical-systems LS3 interfaces lt-1/2/0 unit 3 description LS3->LS2 user@R1# set logical-systems LS3 interfaces lt-1/2/0 unit 3 encapsulation ethernet user@R1# set logical-systems LS3 interfaces lt-1/2/0 unit 3 peer-unit 4 user@R1# set logical-systems LS3 interfaces lt-1/2/0 unit 3 family inet address 10.0.2.1/30 user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 1 description LS2->LS1 user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 1 encapsulation ethernet user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 1 peer-unit 2 user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 1 family inet address 10.0.0.2/30 user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 4 description LS2->LS3 user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 4 encapsulation ethernet user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 4 peer-unit 3 user@R1# set logical-systems LS2 interfaces lt-1/2/0 unit 4 family inet address 10.0.2.2/30 user@R1# set logical-systems LS1 interfaces lt-1/2/0 unit 2 description LS1->LS2 user@R1# set logical-systems LS1 interfaces lt-1/2/0 unit 2 encapsulation ethernet user@R1# set logical-systems LS1 interfaces lt-1/2/0 unit 2 peer-unit 1 user@R1# set logical-systems LS1 interfaces lt-1/2/0 unit 2 family inet address 10.0.0.1/30

2. Enable OSPF on the interfaces.

   [edit]user@R1# set logical-systems LS3 protocols ospf area 0.0.0.0 interface lt-1/2/0.3 user@R1# set logical-systems LS2 protocols ospf area 0.0.0.0 interface lt-1/2/0.1user@R1# set logical-systems LS2 protocols ospf area 0.0.0.0 interface lt-1/2/0.4user@R1# set logical-systems LS1 protocols ospf area 0.0.0.0 interface lt-1/2/0.2

3. Configure the static route on Logical System LS3.

   [edit]user@R1# set logical-systems LS3 routing-options static route 10.0.16.0/30 next-hop 10.0.60.1

4. On Logical System LS3, redistribute the static route into OSPF.

   [edit]user@R1# set logical-systems LS3 protocols ospf export export_static user@R1# set logical-systems LS3 policy-options policy-statement export_static from protocol static user@R1# set logical-systems LS3 policy-options policy-statement export_static then accept

5. On Logical System LS2, configure the OSPF import policy.

   [edit]user@R1# set logical-systems LS2 protocols ospf import filter_routes user@R1# set logical-systems LS2 policy-options policy-statement filter_routes from route-filter 10.0.16.0/30 exact user@R1# set logical-systems LS2 policy-options policy-statement filter_routes then reject

6. If you are done configuring the device, commit the configuration.

   [edit]user@R1# commit

Results

Confirm your configuration by issuing the show logical-systems command.

Verification

Confirm that the configuration is working properly.

• Viewing the OSPF Databases of the Logical Systems
• Viewing the Routing Tables of the Logical Systems

Viewing the OSPF Databases of the Logical Systems

Purpose

Verify that OSPF is advertising the static route.

Action

logical-system: LS2

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router   10.0.0.1         10.0.0.1         0x8000001f   107  0x22 0x8f59  36
Router  *10.0.0.2         10.0.0.2         0x80000025   101  0x22 0x4074  48
Router   10.0.2.1         10.0.2.1         0x80000018   107  0x22 0xab3a  36
Network  10.0.0.1         10.0.0.1         0x80000001   107  0x22 0x7b94  32
Network  10.0.2.1         10.0.2.1         0x8000000c   190  0x22 0x53ab  32
    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Extern   10.0.16.0        10.0.2.1         0x80000007  1785  0x22 0x4147  36
-----
 
logical-system: LS1

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x8000001f   107  0x22 0x8f59  36
Router   10.0.0.2         10.0.0.2         0x80000025   103  0x22 0x4074  48
Router   10.0.2.1         10.0.2.1         0x80000018   109  0x22 0xab3a  36
Network *10.0.0.1         10.0.0.1         0x80000001   107  0x22 0x7b94  32
Network  10.0.2.1         10.0.2.1         0x8000000c   192  0x22 0x53ab  32

    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Extern   10.0.16.0        10.0.2.1         0x80000007  1787  0x22 0x4147  36
-----
 
logical-system: LS3

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router   10.0.0.1         10.0.0.1         0x8000001f   109  0x22 0x8f59  36
Router   10.0.0.2         10.0.0.2         0x80000025   103  0x22 0x4074  48
Router  *10.0.2.1         10.0.2.1         0x80000018   107  0x22 0xab3a  36
Network  10.0.0.1         10.0.0.1         0x80000001   109  0x22 0x7b94  32
Network *10.0.2.1         10.0.2.1         0x8000000c   190  0x22 0x53ab  32

    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Extern  *10.0.16.0        10.0.2.1         0x80000007  1785  0x22 0x4147  36
...

Meaning

The Extern *10.0.16.0 output shows that OSPF is advertising the external route.

Viewing the Routing Tables of the Logical Systems

Purpose

Make sure that Logical System LS3 and Logical System LS1 have the route to the 10.0.16.0/30 network installed in their respective routing tables. Make sure that Logical System LS2 does not have the route installed in its routing table.

Action

logical-system: LS2

inet.0: 5 destinations, 5 routes (5 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.0.0/30        *[Direct/0] 04:22:19
                    > via lt-1/2/0.1
10.0.0.2/32        *[Local/0] 04:22:19
                      Local via lt-1/2/0.1
10.0.2.0/30        *[Direct/0] 04:22:19
                    > via lt-1/2/0.4
10.0.2.2/32        *[Local/0] 04:22:19
                      Local via lt-1/2/0.4
224.0.0.5/32       *[OSPF/10] 04:22:23, metric 1
                      MultiRecv
-----
 
logical-system: LS1

inet.0: 5 destinations, 5 routes (5 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.0.0/30        *[Direct/0] 04:22:19
                    > via lt-1/2/0.2
10.0.0.1/32        *[Local/0] 04:22:19
                      Local via lt-1/2/0.2
10.0.2.0/30        *[OSPF/10] 00:07:52, metric 2
                    > to 10.0.0.2 via lt-1/2/0.2
10.0.16.0/30       *[OSPF/150] 00:07:52, metric 0, tag 0
                    > to 10.0.0.2 via lt-1/2/0.2
224.0.0.5/32       *[OSPF/10] 04:22:23, metric 1
                      MultiRecv
-----
 
logical-system: LS3

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.0.0/30        *[OSPF/10] 00:07:57, metric 2
                    > to 10.0.2.2 via lt-1/2/0.3
10.0.2.0/30        *[Direct/0] 04:22:19
                    > via lt-1/2/0.3
10.0.2.1/32        *[Local/0] 04:22:19
                      Local via lt-1/2/0.3
10.0.16.0/30       *[Static/5] 03:51:18 
                    > to 10.0.60.1 via so-0/0/0.0
10.0.60.0/30       *[Direct/0] 03:53:52
                    > via so-0/0/0.0
10.0.60.2/32       *[Local/0] 03:53:58
                      Local via so-0/0/0.0
224.0.0.5/32       *[OSPF/10] 04:22:23, metric 1
                      MultiRecv

Meaning

The route to 10.0.16.0/30 is not installed in Logical System LS2’s routing table. The route to 10.0.16.0/30 is installed in Logical System LS1’s routing table as a route learned from OSPF. Because it is an OSPF external route, it has a preference value of 150 (instead of 10). By default, routes resulting from OSPF external LSAs are installed with a preference value of 150. The route to 10.0.16.0/30 is installed in Logical System LS3’s routing table as a static route.