Beta Draft Confidential
Configuring Trunks
Configuring VNN OSPF
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/057-57
Configuring VNN OSPF Optimized Flooding
This section describes VNN OSPF optimized flooding and explains how to configure
it in a Lucent switch network.
About VNN OSPF Optimized Flooding
VNN OSPF, like IP OSPF, uses flooding as a reliable way to send LSAs to ensure that
all switches within the same OSPF area have identical link-state databases. Because
multiple copies of each LSA travel through the network, standard OSPF flooding
causes significant network traffic and increases CPU utilization on the switch.
Configuring VNN OSPF optimized flooding enables you to reduce the number of
identical LSAs that are flooded, received, and processed between Lucent switches in
the same area connected by multiple parallel trunks.
To understand the benefits of VNN OSPF optimized flooding, it is helpful to compare
it with how standard OSPF flooding works between switches in the same area
connected by multiple parallel trunks.
Standard OSPF flooding — With standard OSPF flooding, one switch floods an
LSA on all of its parallel trunk interfaces and the other switch receives this LSA on all
of these interfaces. The receiving switch, in turn, floods the same LSA on all of its
parallel trunk interfaces, with the exception of the interface on which it received the
LSA.
As a result, the two switches flood, receive, process, and retransmit multiple copies of
the same LSA throughout the network, while only the original LSA is stored in the
receiving switch’s link-state database. This repeated flooding of identical LSAs
generates significant network traffic, consumes valuable CPU utilization and
bandwidth, and increases the VNN and OSPF database sizes without distributing any
additional topology information.
Note – To configure VNN OSPF optimized flooding, you must be running one of the
following minimum switch software releases:
• CBX 500 switch software Release 08.00.03.00
• GX 550 switch software Release 08.00.03.00
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