LSA of the OSPF protocol

LSA of the OSPF protocol

The LSA concept of the OSPF protocol describes the router Lsarouter LSA Network lsanetwork LSA Network Rollup lsanetwork Summary LSA ASBR Rollup LSAASBR Summary LSA Autonomous System external lsaautonomous System External LSA Group Member Lsagroup membership LSA NSSA external Lsanssa External LSA BGP external Properties External Attributes LSA for BGP opaque LSA Ground link Range opaque LSA opaque LSA Local Zone scope opaque LSA opaque Lsaas range opaque LSA

Concept Introduction Lsa:link State advertisement, link status broadcast. Abr:area BORDER ROUTER. A router that connects multiple zones. asbr:autonomous system Boundary Router, autonomous systems border router. The ASBR is located between the OSPF autonomous system and the non-OSPF network. Router LSA (Router LSA)

LSA No. 1th.
function
All links to the router are advertised, including its status, its cost, and the neighbors of the discovery on that link.
Scope
The router LSA will only hongfan within their own area.
format
Link ID
Depending on the link type, the link ID field represents the same meaning:

LINK Type	Description	meaning of the link ID field
1	Peer Link	Neighbor Router ID
2	Connections to the transit network	Dr's interface address
3	Connections to Stub networks	IP network/Subnet number
4	Virtual link	Neighbor Router ID

NET LSA (network LSA)

function
The DR is generated for each relay broadcast network or NBMA network in the zone. The network LSA lists all the routers that make up the transit network, including the DR itself and the subnet mask of the link.
Scope
Within the region.
format

-The IP address of the Link state id:dr.
-Network mask: The address mask for the broadcast network or NBMA networks.
-attached Router: The Router ID of all routers connected to the same network segment that have a complete adjacency relationship with Dr, also including the Dr itself. NET Rollup LSA (Network Summary LSA)

LSA No. 3rd.
roles & Scopes
Generated by an ABR that advertises networks in its own region to other areas.
After receiving the 1th LSA in its own region, the ABR assembles the number 3rd LSA and sends it out.
format
The format of the network rollup LSA is as follows:

Explanation of some fields:
-Link State ID: For the 3rd LSA, the network address outside the advertised zone. For the 4th LSA, the router ID of the ASBR outside the advertised area.
-The cost of METRIC:ABR yourself to the corresponding LSA destination. When the ABR has multiple routes to the destination, only the lowest cost is sent. Similarly, if an ABR is subject to multiple network rollup LSA in the other LSA, the ABR will also select the least expensive LSA to advertise to the other ABR. ASBR Rollup LSA (ASBR Summary LSA)

LSA No. 4th.
function
The 4th LSA is generated when there is ASBR in the network and is used to provide a route to ASBR. In this way, the data sent to the outside can be found in the ASBR, and sent out.
Scope
The 4th LSA is generated by the ABR. The order is as follows: A ASBR is sent to the number 1th LSA, and the E-bit is set to indicate that it is a asbr. When the ABR receives the LSA, it creates a 4th LSA and spreads to the backbone domain. The other ABR, after receiving the ASBR, spreads it into its own area.
format
The format is the same as 3rd LSA, which indicates identity by marking numbers 3rd or 4th.
-The Link state ID:ASBR routes its ID.
-Network Mask: Fixed set to 0.0.0.0. Autonomous System external LSA (Autonomous System External LSA)

LSA No. 5th.
function
The route used to describe the network to the outside of the OSPF autonomous system.
Scope
Sent by ASBR, and spread to the entire autonomous system.
format
Link State ID: The destination address of the other external as that you want to advertise. E:forwarding Address: Addresses to be forwarded to the address to which the message is to be advertised. External route Tag: Tag added to the external route. OSPF itself does not use the entire field, and he can be used to manage external routes. Group member LSA (membership LSA)

Used in the MOSPF protocol. NSSA External LSA (NSSA External LSA) External properties of BGP (External Attributes LSA for BGP) Opaque LSA (local link range) (Opaque LSA)

LSA 9th, Hongfan only between links. Opaque LSA (local zone Scope) (Opaque LSA)

LSA 10th, Hongfan only within the region. Opaque LSA (as Range) (Opaque LSA)

LSA 11th, Hongfan within the entire OSPF domain.