1. Release 5.1, Revision 0 Copyright © 2001, Juniper Networks, Inc. Advanced Juniper Networks Routing Module 3: OSPF NSSA

2. Copyright © 2001, Juniper Networks, Inc. Module Objectives Review the basic components of the OSPF Protocol Discuss the OSPF neighbor hello protocol and adjacency formation process Examine the function of the Link-State Database (LSDB) and how it contributes routes to the routing table Look at the different kinds of OSPF packet types Configure OSPF on a Juniper Networks router

3. Copyright © 2001, Juniper Networks, Inc. LSA Flooding: Default Backbone (0.0.0.0) Area 1 Area 2 Area 3 External Routes External Routes Area 0 LSA 1 Area 1 LSA 3 Area 0 LSA 5 Area 0 LSA 2 Area 1 LSA 1 Area 1 LSA 2 Area 2 LSA 1 Area 2 LSA 2 Area 3 LSA 1 Area 3 LSA 2 Area 2 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 2 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 1 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 1 LSA 3 Area 2 LSA 3 Area 3 LSA 4 Area 0 LSA 4 Area 3 LSA 4 Area 0 LSA 4 Area 3 LSA 4 Area 0 LSA 4 Area 0 LSA 5 Area 0 LSA 5 Area 0 LSA 5 Area 3 LSA 5 Area 3 LSA 5 Area 3 LSA 5 Area 3 LSA 5

4. Copyright © 2001, Juniper Networks, Inc. OSPF Not-So-Stubby Areas Allows a stub area to contain external routing information from a local ASBR – ASBR injects Type 7 LSAs into NSSA – ABR converts Type 7 to Type 5 and floods into backbone Reachability for other external routes is via a 0/0 default route injected by the ABR – Manual configuration step for administrator control Virtual links can’t transit a NSSA

5. Copyright © 2001, Juniper Networks, Inc. LSA Flooding: NSSA Backbone (0.0.0.0) Area 1 Stub Area 2 Area 3 NSSA External Routes External Routes Area 0 LSA 1 Area 1 LSA 3 Area 0 LSA 5 Area 0 LSA 2 Area 1 LSA 1 Area 1 LSA 2 Area 2 LSA 1 Area 2 LSA 2 Area 3 LSA 1 Area 3 LSA 2 Area 2 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 2 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 1 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 1 LSA 3 Area 2 LSA 3 Area 3 LSA 4 Area 0 LSA 4 Area 3 LSA 4 Area 0 LSA 5 Area 3 LSA 5 Area 3 LSA 7 Area 3 LSA 5

6. Copyright © 2001, Juniper Networks, Inc. OSPF NSSA No-Summaries Behaves like a stub no-summaries area – ABR does not inject Type 3 LSA from backbone into area – ASBR injects Type 7 LSAs into NSSA – ABR converts Type 7 to Type 5 and floods into backbone Reachability for other external routes is still via a 0/0 default route injected by the ABR – Again, a manual configuration step for administrator control Virtual links can’t transit a no-summaries NSSA

7. Copyright © 2001, Juniper Networks, Inc. LSA Flooding: NSSA No-Summaries Backbone (0.0.0.0) Area 1 Stub Area 2 Area 3 NSSA No-Summaries External Routes External Routes Area 0 LSA 1 Area 1 LSA 3 Area 0 LSA 5 Area 0 LSA 2 Area 1 LSA 1 Area 1 LSA 2 Area 2 LSA 1 Area 2 LSA 2 Area 3 LSA 1 Area 3 LSA 2 Area 2 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 2 LSA 3 Area 3 LSA 3 Area 0 LSA 3 Area 1 LSA 3 Area 3 LSA 3 Area 3 LSA 4 Area 0 LSA 4 Area 3 LSA 4 Area 0 LSA 5 Area 3 LSA 7 Area 3 LSA 5 Area 3 LSA 5

8. Copyright © 2001, Juniper Networks, Inc. NSSA Configuration Each router in the area is required to configure itself as a NSSA router The ABR can optionally inject a default route via the default-metric command – Within the default-lsa configuration hierarchy [edit protocols ospf area 0.0.0.1] user@area-1-router# show nssa; interface so-0/0/0.0; [edit protocols ospf area 0.0.0.1] user@area-1-abr# show nssa { default-lsa default-metric 10; } interface so-0/1/1.0;

9. Copyright © 2001, Juniper Networks, Inc. NSSA No-Summaries Configuration Only the ABR is required to configure itself to support a no-summaries area The ABR can optionally inject a default route via the default-metric command – Within the default-lsa configuration hierarchy Default is a Type 3 LSA by default with no-summaries – Can be a Type 7 LSA with the type-7 keyword [edit protocols ospf] user@area-1-abr# show area 0.0.0.1 { nssa { default-lsa { default-metric 10; type-7; } no-summaries; } interface so-0/1/1.0; }

10. Copyright © 2001, Juniper Networks, Inc. Area-Range All ASBR Type 7 routes are forwarded to the backbone by default To summarize routing information, use the area- range command within the NSSA configuration A Type 5 LSA will be injected into the backbone Configured on the ABR only [edit protocols ospf] user@host# set area 1 nssa area-range 192.168.16/20 [edit protocols ospf] user@host# show area 0.0.0.1 { nssa { default-lsa default-metric 10; area-range 192.168.16.0/20; } interface so-0/1/1.0; }

11. Copyright © 2001, Juniper Networks, Inc. Area-Range Restrict Adding the restrict keyword to the area-range command stops all routes in the range from entering the backbone No Type 3 LSA will be injected into the backbone Configured on the ABR only [edit protocols ospf] user@host# set area 1 nssa area-range 192.168.16/20 restrict [edit protocols ospf] user@host# show area 0.0.0.1 { nssa { default-lsa default-metric 10; area-range 192.168.16.0/20 restrict; } interface so-0/1/1.0; }

12. Copyright © 2001, Juniper Networks, Inc. Review Questions What is the difference between area-range in NSSA and a stub area?