LAB: OSPF Resource Limiting

- Configure R4 so that no more than 5000 LSAs can exist in the database.
- No more than 500 of these routes should be originated through
redistribution.
- R4’s OSPF process should be allowed to use up to 20% CPU utilization before allowing interrupts from higher priority processes.

R4:

router ospf 1
max-lsa 5000
redistribute maximum-prefix 500
process-min-time percent 20

LSA prefix limiting is used to prevent against attacks or misconfiguration in the OSPF, which can affect the normal forwarding traffic of the router.  such as full internet bgp table is accidentally redistributed into IGP.  also the process-min-time limits the OSPF's CPU usage.

verification:

Rack1R4#show ip ospf
 Routing Process "ospf 1" with ID 150.1.4.4
 Start time: 00:00:12.492, Time elapsed: 00:12:05.060
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 Supports Link-local Signaling (LLS)
 Supports area transit capability
 Maximum number of non self-generated LSA allowed 5000
    Threshold for warning message 75%
    Ignore-time 5 minutes, reset-time 10 minutes
    Ignore-count allowed 5, current ignore-count 0
 It is an area border and autonomous system boundary router
 Redistributing External Routes from,
    rip, includes subnets in redistribution
    Maximum limit of redistributed prefixes 500
    Threshold for warning message 75%
 Originating router-LSAs with maximum metric
    Condition: always, State: active
 Initial SPF schedule delay 100 msecs
 Minimum hold time between two consecutive SPFs 1000 msecs
 Maximum wait time between two consecutive SPFs 10000 msecs
 Incremental-SPF disabled
 Initial LSA throttle delay 10 msecs
 Minimum hold time for LSA throttle 4000 msecs
 Maximum wait time for LSA throttle 6000 msecs
 Minimum LSA arrival 2000 msecs
 LSA group pacing timer 240 secs
 Interface flood pacing timer 50 msecs
 Retransmission pacing timer 75 msecs
 Number of external LSA 21. Checksum Sum 0x127F78
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 11
 Number of areas in this router is 2. 2 normal 0 stub 0 nssa
 Number of areas transit capable is 0
 External flood list length 0
    Area BACKBONE(0)
        Number of interfaces in this area is 3 (1 loopback)
        Area has no authentication
        SPF algorithm last executed 00:00:46.804 ago
        SPF algorithm executed 4 times
        Area ranges are
        Number of LSA 38. Checksum Sum 0x2BD18A
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 37
        Flood list length 0
    Area 1
        Number of interfaces in this area is 1
        Area has no authentication
        SPF algorithm last executed 00:00:53.592 ago
        SPF algorithm executed 2 times
        Area ranges are
        Number of LSA 93. Checksum Sum 0x4D8CD6
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0