Six LSA types of OSPF

The six main LSA types of OSPF are: the first type. router LSA. router lsa describes the link or interface connected to the physical interface of the ROUTER, and specifies the status and cost of the link. the router in each OSPF area generates the first LSA. it allows routers to know each other's link interfaces. flood occurs only in the generated region. category 2. the Network LSANetwork LSA is initiated by DR. It describes a multi-channel access to all connected routers in the network, and flood occurs only in the generated area. category 3. the network summary LSANetwork summary LSA is issued by the ABR. It informs other regions of the summary of a specific region, that is, to notify the routers in other regions to contact me for these networks. this is a bit far away from the vector routing protocol, which relies on the next hop router for routing. category 4. ASBR summarizes LSAASBR Summary LSA, which is also issued by the ABR, but it tells the routers in other regions to find the ASBR in the announcement for a network not outside the ospf. it can be understood that the summary is generated by the ASBR but advertised by the API on behalf of the owner. it is a type of LSA with special E-bits issued by ASBR, and then forwarded to lsa4. category 5. autonomous system external LSAAutonomous system external LSA ., it is generated by ASBR and used to advertise the routes outside the autonomous system. It is flooding throughout the OSPF autonomous system. therefore, the administrator should try to summarize routes on the ASBR (summary-address external summary network number summary mask) in Class 7. NSSA external LSA refers to the LSA of external AS advertised by ASBR in a non-pure ending area (not-so-stubby area. flood occurs only in this non-pure peripheral area. flood cannot be performed in the entire autonomous system. in The NSSA network, the ABR will convert the 7-class LSA into 5-class LSA and tell the trunk region. region type: Standard region: the default region type. Backbone areas such as the receiving link Update route summary external route are also called transit areas. Other regions are connected to this type. Region 0 is the backbone area. detail area: in this area, the LSA information outside ospf as (Class 5 LSA) cannot be accepted. Only the LSA information between regions and the LSA in this area are accepted, use the default route when you need to access the external. ASBR is not available in the detail area (otherwise, five types of LSA will appear ). if Category 5 LSA is not accepted, no E1 or E2 type route appears in the router table of the region.
To become the standard of the Remote Area: 1. all the routes in the remote area must be configured as the Remote Area Router. Otherwise, the Remote Area Mark in the hello message does not match and thus the neighbor relationship cannot be established. 2. virtual links cannot exist in the last section. ASBR4. the last region can only have one region exit or multiple zones exit, but you do not need to select the optimal path. in the default type, the overhead (E2 type) in OSPF is not considered for the route from the router to the external AS. Therefore, the optimal path cannot be selected. absolute detail area: CISCO proprietary enhanced version based on the detail area, which not only does not accept 5 types of LSA. do not accept the summary LSA for Category 3 and Category 4. therefore, there will be no o ia E1 E2 type routing in the route table in the last section. ASBR cannot exist in the absolute detail area. A non-pure detail area is also called a subdetail area. NSSA region, which is a kind of abnormal extension of the detail area. It allows ASBR to appear in the detail section, so there is a unique 7 nssa lsa in this region.
Comparison tables of LSA types in various regions: www.2cto.com region type 1 & 2 3 & 4 5 7 backbone regions allow non-existent standard areas allow non-existent sub-areas allow 3 allow/4 do not allow non-existent absolute sub-areas allow not allowed * (only 0.0.0.0 is the default sum) NSSA (minor region) is not allowed. 3 is allowed./4 is not allowed. # Allow * use three types of LSA to advertise the default route on the ABR. This is an exception. # execute 7-to-5 (for LSA with P-bit = 1 set for 7 classes) on The nssa api, and execute the 7-to-5 API to become a special combination of ABR/ASBR, there are five types of routers. Note that the five types are not related to the region. DR is a designated vro designed to solve LSA's waste of bandwidth in an area. BDR is a backup of the specified vro, which is a backup of DR. DR and BDR are available only in the broadcast network and NBMA network, but not in P2P and P2MP networks. An API is a regional border router. It is a router between two OSPF regions and is mainly used to transmit routes between two regions. An ASBR is a Autonomous System border router that is located between two AS routers, it is mainly used to transmit routes between two autonomous systems.