Let’s wrap up the OSPF series with some features that are less common but might still be ask during the CCIE LAB.
Mostly use for on-demand circuit such as ISDN.
With this feature, periodic hellos are suppressed and the periodic refreshes of LSAs are not flooded over the demand circuit.
Periodic refreshes of hello updates, LSA updates, and other protocol overhead are prevented from enabling the on-demand circuit when there is no “real” data to send.
R1(config)#int Ethernet0/0 R1(config-if)#ip ospf demand-circuit R1#sh ip ospf int Ethernet0/0 Ethernet0/0 is up, line protocol is up Internet Address 10.10.1.1/24, Area 0, Attached via Interface Enable Process ID 10, Router ID 184.108.40.206, Network Type BROADCAST, Cost: 1 SNIP Configured as demand circuit Run as demand circuit DoNotAge LSA allowed
This feature will stop the “paranoid update”.
It stops unnecessary LSA flooding by setting the DoNotAge (DNA) bit in the LSA, so there is no need for periodic refresh.
R1(config)#int Ethernet0/0 R1(config-if)#ip ospf flood-reduction R1#sh ip ospf int Ethernet0/0 Ethernet0/0 is up, line protocol is up Internet Address 10.10.1.1/24, Area 0, Attached via Interface Enable SNIP Enabled by interface config, including secondary ip addresses Reduce LSA flooding.
This feature is use to restrict the number of prefixes redistributed in OSPF and the number of LSA in the OSPF database.
R5(config)#router ospf 10 R5(config-router)#max-lsa ? Maximum number of non self-generated LSAs this process can receive R5(config-router)#max-lsa 10 *Feb 25 14:25:32.510: %OSPF-4-OSPF_MAX_LSA_THR: Threshold for maximum number of non self-generated LSA has been reached "ospf 10" - 7 LSAs *Feb 25 14:25:32.510: %OSPF-4-OSPF_MAX_LSA: Maximum number of non self-generated LSA has been exceeded "ospf 10" - 26 LSAs R5(config-router)#redistribute maximum-prefix 2 R5#sh ip ospf 10 Routing Process "ospf 10" with ID 220.127.116.11 SNIP Redistributing External Routes from, connected, includes subnets in redistribution Maximum limit of redistributed prefixes 2 Threshold for warning message 75%
That’s all for OSPF.
Thank you for reading.