To stop type 7 LSAs from being injected into area 1, the no-nssa-abr statement in included in the Device 4 configuration. From operational mode on Device 1 and Device 6, enter the show route command. The customer routes and have been learned from Device 2. The and routes have been suppressed. They are not needed because the default route can be used instead. From operational mode on Device 1, enter the show ospf3 database nssa detail command. OSPF requires that all areas in an autonomous system AS must be physically connected to the backbone area area 0.
Virtual links use a transit area that contains two or more area border routers ABRs to pass network traffic from one adjacent area to another. The transit area must have full routing information and it cannot be a stub area. For example, Figure 13 shows a virtual link between a noncontiguous area and the backbone area through an area connected to both. In the topology shown in Figure 13 , a virtual link is established between area 0.
The virtual link transits area 0. This example shows how to configure an OSPF virtual link to connect noncontiguous areas. If any routing device on the backbone is not physically connected to the backbone, you must establish a virtual connection between that routing device and the backbone to connect the noncontiguous areas. These routing devices must be area border routers ABRs , with one that is physically connected to the backbone.
You cannot configure virtual links through stub areas. You must also specify the number of the area through which the virtual link transits also known as the transit area. You apply these settings to the backbone area defined by the area 0.
In this example, Device R1 and Device R2 are the routing devices at each end of the virtual link, with Device R1 physically connected to the backbone, as shown in Figure You configure the following virtual link settings:. In this example, Device R1 has a router ID of In this example, area 0.
Area 0. You must configure both routing devices that are part of the virtual link and specify the applicable neighbor ID on each routing device. For an OSPFv3 virtual link, include the ospf3 statement at the [edit protocols] hierarchy level. Configure an OSPF virtual link and specify the transit area 0.
This routing device must be an ABR that is physically connected to the backbone. This routing device is not physically connected to the backbone. Confirm your configuration by entering the show routing-options and the show protocols ospf commands.
If configured as a virtual link, the Type is Virtual. The Type field displays the type of interface. If the interface is configured as part of a virtual link, the Type is Virtual. When an area lacks an adjacency with area 0, a virtual link is required to connect to the backbone through a non-backbone area.
The area through which you configure the virtual link, known as a transit area, must have full routing information. The transit area cannot be a stub area. Figure 15 shows the topology used in this example. Device 2, Device 3, and Device 4 connect to each other across Area 1.
Because Device 5 does not have a direct adjacency to Area 0, a virtual link is required across Area 1 between Device 3 and Device 4. Similarly, because Device 0 and Device 1 have two separate Area 0 backbone sections, you need to configure a second virtual link across Area 1 between Device 2 and Device 3.
Configure two virtual links through Area 1—one connecting to Device 2 and the second connecting to Device 4. From configuration mode, confirm your configuration by entering the show interfaces , show protocols , and show routing-options commands. If you are done configuring the devices, enter commit from configuration mode.
To view prefix information, you must use the extensive option with the show ospf3 database command. Verify that Device 0 has learned the expected routes and has established the expected neighbor adjacencies.
These routes are the routes that are installed in the routing table. Verify that Device 1 has learned the expected routes and has established the expected neighbor adjacencies. Verify that Device 2 has learned the expected routes and has established the expected neighbor adjacencies. Verify that Device 3 has learned the expected routes and has established the expected neighbor adjacencies.
Verify that Device 4 has learned the expected routes and has established the expected neighbor adjacencies. Verify that Device 5 has learned the expected routes and has established the expected neighbor adjacencies. Help us improve your experience. Let us know what you think. Do you have time for a two-minute survey? Maybe Later. Areas An area is a set of networks and hosts within an AS that have been administratively grouped together.
All routing devices within an area have identical topology databases. Stub Areas Stub areas are areas through which or into which AS external advertisements are not flooded. Transit Areas Transit areas are used to pass traffic from one adjacent area to the backbone or to another area if the backbone is more than two hops away from an area. Each multiaccess network has a designated router, which performs two main functions: Originate network link advertisements on behalf of the network.
Overview The router identifier is used by OSPF to identify the routing device from which a packet originated. Junos OS selects a router identifier according to the following set of rules: By default, Junos OS selects the lowest configured physical IP address of an interface as the router identifier. Note: 1. Configuration CLI Quick Configuration Procedure Results CLI Quick Configuration To quickly configure an OSPF router identifier, 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.
Results Confirm your configuration by entering the show routing-options router-id command. Requirements Before you begin: Configure the device interfaces.
Configuration CLI Quick Configuration Procedure Results CLI Quick Configuration To quickly configure an OSPF designated router election, 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. Note: To specify an OSPFv3 interface, include the ospf3 statement at the [edit protocols] hierarchy level.
Results Confirm your configuration by entering the show protocols ospf command. Verification Confirm that the configuration is working properly.
Action From operational mode, enter the show ospf interface and the show ospf neighbor commands for OSPFv2, and enter the show ospf3 interface and the show ospf3 neighbor commands for OSPFv3. Configuration CLI Quick Configuration Procedure Results CLI Quick Configuration To quickly configure a single-area OSPF network, 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.
Note: For a single-area OSPFv3 network, include the ospf3 statement at the [edit protocols] hierarchy level. Configuration Procedure Results Procedure CLI Quick Configuration Step-by-Step Procedure CLI Quick Configuration To quickly configure a multiarea OSPF network, 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.
Device A [edit] set protocols ospf area 0. Note: For a multiarea OSPFv3 network, include the ospf3 statement at the [edit protocols] hierarchy level.
When configuring a secondary interface, consider the following: For OSPFv2, you cannot configure point-to-multipoint and nonbroadcast multiaccess NBMA network interfaces as a secondary interface because secondary interfaces are treated as a point-to-point unnumbered link.
You cannot configure a secondary interface by its IP address. Configuration CLI Quick Configuration Procedure Results CLI Quick Configuration To quickly configure a secondary logical interface for an OSPF area, 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.
Procedure Step-by-Step Procedure To configure a secondary logical interface: Configure the device interfaces. Results Confirm your configuration by entering the show interfaces , show routing-options , and the show protocols ospf commands. Requirements No special configuration beyond device initialization is required before configuring this example.
Overview OSPFv3 intra-area paths are preferred over inter-area paths. Clearly, this scenario results in suboptimal routing. Configuration Procedure CLI Quick Configuration Step-by-Step Procedure Step-by-Step Procedure Results 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. To configure Device R1: Configure the interfaces. To configure Device R2: Configure the interfaces. Results From configuration mode, confirm your configuration by entering the show interfaces and show protocols commands.
Meaning The traceroute output shows that traffic uses the link between Device R1 and Device R2. Action Deactivate the backbone link interfaces in area 1.
Meaning Without the multiarea adjacency, the output shows suboptimal routing with traffic taking the path through the area 1 low-speed-links. Note: If you incorrectly configure a totally stubby area, you might encounter network connectivity issues. Overview The backbone area, which is 0 in Figure 8 , has a special function and is always assigned the area ID 0.
The following restrictions apply to stub areas: You cannot create a virtual link through a stub area. A stub area cannot contain an AS boundary router. You cannot configure the backbone as a stub area. You cannot configure an area as both a stub area and an not-so-stubby area NSSA. Note: To specify an OSPFv3 stub area, include the ospf3 statement at the [edit protocols] hierarchy level.
Configuration on all routing devices: user host show protocols ospf area 0. Overview The backbone area, which is 0 in Figure 9 , has a special function and is always assigned the area ID 0. Configuration on all routing devices in the area: user host show protocols ospf area 0. Overview Figure 10 shows the topology used in this example. Using the information from its topology database. Dijkstra in OSPF will then construct three tables to store the following information:.
It means dividing routers inside a single autonomous system running OSPF, into areas where each area consists of a group of connected routers. The idea of dividing the OSPF network into areas is to simplify administration and optimize available resources.
Resource optimization is especially important for large enterprise networks with a plethora of network and links. Use the area area-id virtual-link router-id command in order to configure a virtual link, where the area-id is the area ID assigned to the transit area this can be either a valid IP address or a decimal value , and where router-id is the router ID associated with the virtual link neighbor.
In this example, the virtual link connects area 7 to the backbone through area In this example, the virtual link is created between the routers with router ID 1. In order to create the virtual link, configure the area 5 virtual-link 2.
Skip to content Skip to search Skip to footer. Available Languages. Download Options. Updated: February 25, Contents Introduction. Each OSPF network that is divided into different areas must follow these rules: A backbone area - which combines a set of independent areas into a single domain - must exist. Define a Stub Area Use the area xx stub command in every router in the area to define an area as a stub area.
What Are Virtual Links? In this example, the virtual link connects area 7 to the backbone through area 5: In this example, the virtual link is created between the routers with router ID 1.
Contributed by Cisco Engineers. However, with Totally stubby areas the Type 3 inter-area advertisement is also removed, and a single default route is injected by the ABR. NSSA's can function as either stub shown above , or totally stubby area's. Accessed 14 Nov. Check your inbox and click the link to complete signin. Check your inbox and click the link to confirm your subscription. What is DPDK?
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