Shulou(Shulou.com)06/03 Report--

Themes:

OSPF multi-area configuration

ABR:area border router, area border router-functions to interwork between different areas;-defines routers that connect both backbone and non-backbone areas; why does OSPF introduce / partition areas? After dividing the area, you can bring the following benefits: 1. Save the system resources of each device in the area (after the large area is divided, the database content in the small area becomes less) (all routers in the same area The database is exactly the same) 2. Enhance the stability of the OSPF network (the adverse effects caused by an unstable link, only in the same area) (spread in, will not affect other areas)

During the verification process:

1. Some route entries do not reflect the real network address of the corresponding port;-> network type

2. In Huawei equipment, the administrative distance (preference) of OSPF is 10; a metric, called cost (cost)

Routing protocol-route declaration method

1. Network: those who enter the protocol in this way are called internal routing.

In LS routing protocol, internal routing is subdivided into intra-area and inter-area.

2. Import-route: if you enter the protocol by way, we call it external routing.

(redistribute Cisco) in the LS protocol, external routes are divided into type 1 and type 2, with a default of 2

Topology configuration: 1. OSPF establish neighbors; (manually specify OSPF RID) display ospf peer brief 2, verify neighbor table and routing table display ospf peer brief display ip routing-table3, view and change the network type of loopback 0 Display ospf interface loopback 0 interface loopback 0 ospf network-type broadcast4, view the breakdown type of OSFP routes display ospf routing 5, verify ASE type routes-leads to the "route declaration" method: network / import-route6, configure static routes on R4, then import-route, view on other routers R4: ip rout-static 100.1.1.0 255.255.255.0 null 0 ospf 1 import-route static R3: display ip routing-table display ospf routing

OSPF normal area

LSA-link state advertisment Class 5 LSA-represents "external routing";-the transmission range is unlimited and can be transmitted to the entire network of OSPF

OSPF special area

-refers to areas where type 5 LSA is not allowed.

-Classification # stub area: type 4 or 5 LSA is not allowed in this area, so all routers in this area do not have external routes, so, in order to communicate with external routes, the ABR of the stub area automatically generates a default route to the stub. And belongs to the inter-area of OSPF. -configuration command: # need to configure each router in this area # configuration is as follows: ospf 1 area 34 stub # totally stub region: complete stub area. Type 3, 4 and 5 LSA are not allowed in this area (only a special type 3 LSA is retained. Indicates a default route) can reduce the size of the database in the stub area At the same time, it can also reduce the instability in other regions and the adverse impact on the region. # nssa region: not so stub area. # totally nssa region is not allowed in this region: full NSSA region

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Type of LSA: type 1 LSA-router lsa, any OSPF router will generate a Class 1 LSA in any area. It is equivalent to the self-introduction of a router in a specific area. Based on the type 1 LSA calculated route, we call it intra-area route. Type 2 LSA-3 type LSA-summary-network can only be produced by ABR; its function is to transfer routes between different areas; based on the routes calculated by three types of LSA, we call them inter-area routes. Generation of type 3 LSA: ABR will change the route in the non-backbone area into the form of type 3 LSA, and the ABR in the backbone area will continue to send the type 3 LSA received in area 0 to other non-backbone areas. ARB can also change the route in area 0 into the form of type 3 LSA, sending non-backbone area type 3 LSA in the transmission process, each passing through an ABR, the "advertisement router" will change. Type 4 LSA-this LSA exists only to cooperate with type 5 LSA to calculate external routes; it is generated by ABR in the same area as ASBR; the transmission process is similar to type 3 LSA, where the "advertisement router" changes every time an ABR passes. Type 5 LSA-as external lsa can only be generated by ASBR, which represents an external route and can be transmitted anywhere in the OSPF network. And in the process of transmission, LSA will not produce any change. OSPF basic theory, single-area configuration OSPF multi-area configuration, ABR, ospf routing type internal: declared by network Intra-area inter-area external: announced by redistribution (redistribute | import-route) # Class 5 LSA can be transmitted anywhere in the OSPF network Special areas: 5 types of LSA-stub: 4 and 5 types are not allowed The ABR of the area automatically generates a default route (inter-area) to the area. All routers in the area need to be configured with stub. Ospf 1 area 34 stub-totally stub: type 3, 4 and 5 LSA are not allowed in complete stub areas But there is a special three types of LSA Indicates that the default route only needs to be configured on ABR in the stub area at this time: ospf 1 area 34 stub no-summary Normal area:-Type 1 of LSA-any OSPF router will generate, Will be generated in every area connected. The route calculated by type 1 LSA belongs to intra-area route; 2-3-only ABR can be generated (0 [intra-area / inter-area]-- > non-0; non-0 [intra-area]-- > 0 ) represents the route between areas, and the LSA changes during transmission: each time an ABR passes, the advertised router changes. 4-5-only ASBR can be generated; represents an external route, and the LSA is unchanged during transmission; prefix/mask [preference/cost] type, via next-hop, interfaceOSPF special area: NSSA: no so stub area, this area does not allow type 4 or 5 LSA, but allows external routes to exist External routes are represented by type-7 LSA. 7 types of LSA can only exist in the NSSA region. That is, only 1, 2, 3, 7-Application scenarios-configuration: NSSA is configured on every router in the area. Ospf 1 area 14 nssa the ABR of this area will automatically generate a default route to the NSSA area, which is represented by type 7 LSA, and the ABR of this area will convert the external route represented by type 7 LSA into type 5 LSA, so that other OSPF areas (normal) can obtain the external route entry. And in the one-way conversion of 7 to 5, only the ABR with large RID in the NSSA area can be finally converted. Compared with NSSA, totally NSSA also lacks three types of detailed routes represented by LSA, that is, there are only 1, 2, 7; only through a default route represented by type 7 LSA automatically generated by ABR in NSSA area, the interworking between NSSA area and other areas and external routes can be realized. Configuration command: just need to do it in all the ABR in the NSSA area. Ospf 1 area 14 nssa no-summary OSPF discontiguous area solution:-construct ABR so that routes to this non-backbone area exist as internal routes in other areas; # on routers connecting multiple non-backbone areas, an OSPF neighbor relationship with area 0 is established by re-linking a "physical link" The OSPF neighbor relationship established by # virtual-link through the virtual link always belongs to area 0; the establishment of the virtual link depends on the area where the underlying real link is located to transmit OSPF packets (hello, etc.). Therefore, if the underlying "traversal / transmission area" is unstable, it will lead to the instability of the upper "virtual link", which will affect the stability of the backbone area of the whole network. Therefore, this approach is generally not recommended. If you have to use it, it's only a temporary solution. -configuration: configure the following command in the real ABR of the router and transport area that wants to be ABR: R1: ospf 1 area 14 vlink-peer 4.4.4.4 / / here It must be the RID R4 of the other router: ospf 1 area 14 vlink-peer 1.1.1.1 / / must not be written as the interface IP of the other device. You must ensure that the OSPF neighbor relationship in area 14 is intact. Display ospf vlink / / look at the OSFP neighbor relationships established locally over virtual links-build different OSPF processes so that the delivery of routes is presented as external routes. R4: create a new OSPF process-ospf 8 ospf 8 / / R4 establishes a neighbor relationship with R7 through ospf 8. Area 47 network 192.168.47.4 0.0.0.0 quit import-route ospf 1 ospf 1 / / R4 establishes a neighbor relationship with R1 through ospf 1. Import-route ospf 8

Analysis of OSPF LSA:

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