Filter
Top Products
Configuring OSPF
Blocking OSPF LSA Flooding
IPC-237
Cisco IOS IP Configuration Guide
Figure 40 OSPF LSAs on Individual Timers with Group Pacing
The group pacing interval is inversely proportional to the number of LSAs the router is refreshing,
checksumming, and aging. For example, if you have approximately 10,000 LSAs, decreasing the pacing
interval would benefit you. If you have a very small database (40 to 100 LSAs), increasing the pacing
interval to 10 to 20 minutes might benefit you slightly.
The default value of pacing between LSA groups is 240 seconds (4 minutes). The range is from 10
seconds to 1800 seconds (30 minutes). To change the LSA group pacing interval, use the following
command in router configuration mode:
For an example, see the section “LSA Group Pacing Example” at the end of this chapter.
Blocking OSPF LSA Flooding
By default, OSPF floods new LSAs over all interfaces in the same area, except the interface on which
the LSA arrives. Some redundancy is desirable, because it ensures robust flooding. However, too much
redundancy can waste bandwidth and might destabilize the network due to excessive link and CPU usage
in certain topologies. An example would be a fully meshed topology.
You can block OSPF flooding of LSAs two ways, depending on the type of networks:
• On broadcast, nonbroadcast, and point-to-point networks, you can block flooding over specified
OSPF interfaces.
• On point-to-multipoint networks, you can block flooding to a specified neighbor.
On broadcast, nonbroadcast, and point-to-point networks, to prevent flooding of OSPF LSAs, use the
following command in interface configuration mode:
4 min
Individual LSA timers with group pacing
20 LSAs, 1 packet
15 LSAs, 1 packet
10471
37 LSAs, 1 packet
4 min 4 min
É
Individual LSA timers
and at random intervals. Individual LSA timers require many
refresh packets that contain few LSAs.
Command Purpose
Router(config-router)# timers lsa-group-pacing
seconds
Changes the group pacing of LSAs.