# OSPF prefix-suppression vs. OSPF distribute-list **URL:** \ **Category:** CCNP Enterprise\ **Tags:** networking, ine, security, lab\ **Created:** [May 21, 2023, 10:00am UTC](https://legacy-community.ine.com/t/ospf-prefix-suppression-vs-ospf-distribute-list/3745 "2023-05-21T10:00:40Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![major133-ac9365513dd](https://avatars.discourse-cdn.com/v4/letter/m/f4b2a3/32.png) [@major133-ac9365513dd](https://legacy-community.ine.com/u/major133-ac9365513dd)\ **Post date:** [May 21, 2023, 10:00am UTC](https://legacy-community.ine.com/t/ospf-prefix-suppression-vs-ospf-distribute-list/3745/1 "2023-05-21T10:00:40Z")
Hi @Network_Eric ![OSPF Topology](https://us1.discourse-cdn.com/flex015/uploads/ine/original/1X/6662a3d87c460cee606fb6d5ce2a6ecc6355a2ed.png) in order to do filtering on R3`s global routing table to have 10.1.12.0/24 we have two solutions :- 1-prefix-suppression 2-do ospf route-filtering for 10.1.12.0/24 which means we need to do route filtering for routes are within the same area. let`s do the the first way: 1. R1#show running-config interface fastEthernet 0/0.12 2. interface FastEthernet0/0.12 3. encapsulation dot1Q 12 4. ip address 10.1.12.1 255.255.255.0 5. ip ospf network point-to-point 6. ip ospf prefix-suppression R2#show running-config interface fastEthernet 0/0.12 interface FastEthernet0/0.12 encapsulation dot1Q 12 ip address 10.1.12.2 255.255.255.0 ip ospf network point-to-point ip ospf prefix-suppression R3#show ip route ospf | begin Ga Gateway of last resort is not set ``` 1.0.0.0/32 is subnetted, 1 subnets ``` O 1.1.1.1 [110/3] via 10.1.23.2, 00:00:04, FastEthernet0/0.23 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/2] via 10.1.23.2, 00:00:04, FastEthernet0/0.23 now let`s do the second solution R1(config)#interface fastEthernet 0/0.12 R1(config-subif)#ip ospf prefix-suppression disable R2(config)#interface fastEthernet 0/0.12 R2(config-subif)#ip ospf prefix-suppression disable R3(config)#ip access-list standard test R3(config-std-nacl)#deny 10.1.12.0 0.0.0.255 R3(config-std-nacl)#permit any R3(config)#router ospf 1 R3(config-router)#distribute-list test in R3#show ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/3] via 10.1.23.2, 00:00:09, FastEthernet0/0.23 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/2] via 10.1.23.2, 00:00:09, FastEthernet0/0.23 ok,everything is working as expected but the question is, what is the difference between the first solution and the second solution? R3(config)#router ospf 1 R3(config-router)#no distribute-list test in R3#show ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/3] via 10.1.23.2, 00:00:19, FastEthernet0/0.23 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/2] via 10.1.23.2, 00:00:19, FastEthernet0/0.23 10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks O 10.1.12.0/24 [110/2] via 10.1.23.2, 00:00:19, FastEthernet0/0.23 another question , why i see 10.1.12.0/24 only one time in the routing table? why i don`t see it two times from R1 and R2 ? another question, why the loo0 for R1 cost =3 but the loo0 R2 cost=2?why both are not have cost=2 on R3? ---
**Author:** ![major133-ac9365513dd](https://avatars.discourse-cdn.com/v4/letter/m/f4b2a3/32.png) [@major133-ac9365513dd](https://legacy-community.ine.com/u/major133-ac9365513dd)\ **Post date:** [May 22, 2023, 4:52pm UTC](https://legacy-community.ine.com/t/ospf-prefix-suppression-vs-ospf-distribute-list/3745/2 "2023-05-22T16:52:52Z")
@Network_Eric ![PBR feature](https://us1.discourse-cdn.com/flex015/uploads/ine/original/1X/3b24124cccba162f6a80d5c36e4af2f3815dde87.png) is the second bullet is correct or not ? i could apply the PBR feature for the packets are locally originated