Ospf Rfc 1583 And 2328 Compliance; Reduction Of Equivalent As External Lsas - HP ProCurve 6200yl Multicast And Routing Manual

N o t e
When multiple ProCurve switches on the same network are declaring them-
selves as DRs, then both priority and router ID are used to select the desig­
nated router and backup designated routers.
When only one router on the network claims the DR role despite neighboring
routers with higher priorities or router IDs, this router remains the DR. This
is also true for BDRs.
The DR and BDR election process is performed when one of the following
events occurs:
■ an interface is in a waiting state and the wait time expires
■ an interface is in a waiting state and a hello packet is received that
addresses the BDR
a change in the neighbor state occurs, such as:
■
• a neighbor state transitions from 2 or higher
• communication to a neighbor is lost
• a neighbor declares itself to be the DR or BDR for the first time

OSPF RFC 1583 and 2328 Compliance

The switches covered in this guide are configured, by default, to be compliant
with the RFC 1583 OSPF V2 specification. These switches can also be config­
ured to operate with the latest OSPF standard, RFC 2328.
For details on how to configure the system to operate with the RFC 2328, see
"Configuring OSPF" on page 5-39.

Reduction of Equivalent AS External LSAs

An OSPF ASBR uses AS External link advertisements (AS External LSAs) to
originate advertisements of a route to another routing domain, such as a RIP
domain. The ASBR advertises the route to the external domain by flooding AS
External LSAs to all the other OSPF routers (except those inside stub
networks) within the local OSPF Autonomous System (AS).
In some cases, multiple ASBRs in an AS can originate equivalent LSAs. The
LSAs are equivalent when they have the same cost, the same next hop, and
the same destination. The ProCurve switch optimizes OSPF by eliminating
duplicate AS External LSAs in this case. The switch with the lower router ID
flushes the duplicate External LSAs from its database and thus does not flood
the duplicate External LSAs into the OSPF AS. AS External LSA reduction
therefore reduces the size of the switch's link state database.
IP Routing Features
Configuring OSPF
5-37