OSPF Configuration
Overview of OSPF features supported by the IP2000
Stinger®
IP2000 Configuration Guide
6-3
routers and networks forms the OSPF topological database. Table 6-1 shows the types
of LSAs.
Designated and backup designated routers on broadcast networks
In OSPF terminology, a broadcast network is any network that has more than two
OSPF routers attached and supports the capability to address a single physical
message to all the attached routers (broadcast). Neighboring routers are discovered
dynamically on these networks using the OSPF Hello protocol, which uses the
broadcast capability. Ethernet is an example of a broadcast network. Figure 6-1
shows such a network.
Figure 6-1. OSPF broadcast network on Gigabit Ethernet
Table 6-1. Description of LSA types
LSA type
Description
Type 1 (RTR) router
Type 1 LSAs describe the collected states of the router’s
interfaces.
Type 2 (NET) network
Type 2 LSAs describe the set of routers attached to the
network.
Types 3 and 4
(Summary LSAs)
Summary LSAs are flooded throughout a single area.
Type 3 summary LSAs describe routes to networks.
Type 4 summary LSAs describe routes to autonomous
system boundary routers.
Type 5 (ASE) AS-external
Type 5 LSAs describe routes to destinations external to
the autonomous system (AS). An AS-external-LSA can
also describe a default route for the autonomous
system. For example, other routers send LSAs to only
the designated router by using the All-Designated-
Routers multicast address of 224.0.0.6.
Type 7 (ASE) NSSA
NSSAs are like stub areas in that they do not receive or
originate type 5 LSAs. However, NSSAs rely solely on
default routing for external routes. They employ type 7
LSAs for carrying ASE route information within the
area. Type 7 LSAs use a propagate (P) bit to flag the
NSSA border router to translate the type 7 LSA into a
type 5 LSA, which can then be propagated into other
areas.
Backup
designated
router (BDR)
Designated
router (DR)
Gigabit
Ethernet
