OSPF Database Overflow
Definition
OSPF requires that routers in the same area have the same Link-State Database (LSDB).
With the continuous increase in routes on the network, some routers fail to carry the additional routing information because of limited system resources. This situation is called OSPF database overflow.
Purpose
You can configure stub areas or NSSAs to solve the problem of the continuous increase in routing information that causes the exhaustion of system resources of routers. However, configuring stub areas or NSSAs cannot solve the problem when the unexpected increase in dynamic routes causes database overflow. Setting the maximum number of external LSAs in the LSDB can dynamically limit the LSDB capacity, to avoid the problems caused by database overflow.
Principle
To prevent database overflow, you can set the maximum number of non-default external routes on a router.
All routers on the OSPF network must be set with the same upper limit. If the number of external routes on a router reaches the upper limit, the router enters the Overflow state and starts an overflow timer. The router automatically exits from the overflow state after the timer expires. By default, it is 5 seconds.
Overflow Phase |
OSPF Processing |
|---|---|
Entering overflow state |
A router deletes all non-default external routes that are generated. |
Staying in overflow state |
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Exiting from the overflow state |
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