#Ospf network types update#

LSA Type 7 – OSPF Not So Stubby Area (NSSA) External LSA MOSPF is not supported by Cisco and is not widely used and is expected to be retired soon. LSA Type 6 ( Group Membership LSA) packets were designed for Multicast OSPF (MOSPF), a protocol that supports multicast routing through OSPF. This external route/prefix is redistributed in to the OSPF network by the ASBR ( R1) and seen as O E1 or E2 entries in other OSPF routers routing tables. LSA Type 5 packets advertise the default route to all OSPF routers A typical example of an LSA Type 5 would be an external prefix e.g 192.168.10.0/24 or default route (internet) as shown below:įigure 6. LSA Type 5 ( ASBR External LSA) packets are generated by the ASBR to advertise external redistributed routes into the OSPF’s AS. While LSA Type 4 packets are used by ABRs to advertise the ASBR route through their areas, it will not be used by the ASBR itself within its local area ( Area 1) ASBR uses LSA Type 1 to inform its neighbors ( R2 in this case) within its networks. LSA Type 4 packets injected into Area 0 & 2 by the R2 ABR and R3 ABR In the example below when R2 ( ABR) receives the LSA Type 1 packet from R1 it will create a LSA Type 4 ( Summary ASBR LSA) packet, which advertises the ASBR route received from Area 1, and inject it into Area 0.įigure 5. LSA Type 4 ( ASBR Summary LSA) packets are the LSAs that advertise the presence of an Autonomous System Border Router ( ASBR) to other areas. Type 3 Summary LSAs appear as O IA entries in the router routing table. In a similar way, ABR router R3 creates a Type 3 Summary LSA and floods it into Area 2.

Looking at the diagram above, ABR router R2 creates a Type 3 Summary LSA and floods it into Area 0. LSA Type 3 - An OSPF ABR router advertises the summarized route 192.168.2.0/24 to Area 0 LSA Type 3 packets are flooded to multiple areas throughout the network and help with OSPF’s scalability with the use of summary prefixes.įigure 4. LSA Type 3 ( Summary LSA) packets are generated by Area Border Routers ( ABR) to summarize its directly connected area, and advertise inter-area router information to other areas the ABR is connected to, with the use of a summary prefix (e.g 192.168.0.0/22). LSA Type 2 Packets exchanged between OSPF DR and neighbor routers LSA Type 3 – OSPF Summary LSA LSA Type 2 packets are flooded between neighbors in the same area of origin and remain within that area.įigure 3. LSA Type 2 ( Network LSA) packets are generated by the Designated Router ( DR) to describe all routers connected to its segment directly. LSA Type 1 Packets exchanged between OSPF routers within the same area LSA Type 2 – OSPF Network LSA An OSPF router uses LSA Type 1 packets to describe its own interfaces but also carries information about its neighbors to adjacent routers in the same area.įigure 2. LSA Type 1 ( Router LSA) packets are sent between routers within the same area of origin and do not leave the area. This article assumes the reader has a good understanding of basic OSPF theory and is comfortable with OSPF concepts. OSPF concepts, including router roles such as Designated Router ( DR), Area Border Router ( ABR), Autonomous System Border Router ( ASBR), OSPF Areas and more, are analyzed in great depth in our article OSPF Basic Concepts – OSPF Areas – Router Roles. Each LSA is used within specific boundaries of an OSPF network. LSA Types contained within an OSPF LSU packetĪs mentioned, OSPF currently supports 11 types of LSAs. The diagram below clearly shows how LSAs are contained within LSUs:įigure 1. The LSA payload varies in size according to the LSA type and the information it includes. LSA Type 11:OSPF AS (Autonomous System) Scope Opaque LSA.LSA Type 10: OSPF Area Scope Opaque LSA.LSA Type 9: OSPF Link Scope Opaque (OSPFv2) / Intra Area Prefix LSA (OSPFv3).LSA Type 8: OSPF External Attributes LSA (OSPFv2) / Link Local LSA (OSPFv3).LSA Type 7: OSPF Not So Stubby Area (NSSA) External LSA.LSA Types - Quick Overviewīefore we begin, let’s take a quick look at the different type of OSPF LSA packets we’ll cover:

In this article we’ll be diving deeper to analyse all eleven OSPF LSA Types using network network diagrams and examples to help understand when each LSA type is used and how they keep the OSPF network updated. We also saw the most common LSA packets found in OSPF networks.

#Ospf network types update#

Our previous article explained the purpose of Link State Update (LSU) packets and examined the Link State Advertisement ( LSA) information contained within LSU packets.