Exam 350-401 topic 1 question 677 discussion

I would think prefix suppression would be better if placed on R2 on the interface facing R4. Being applied globally on R1 won't suppress routes from other routers to R4. Like to see what others think. https://itskillbuilding.com/networking/network/ospf/ospf-prefix-suppression/

I simulated this topology and the correct answer is A. Only prefix-suppression on R1(DR) under router ospf 1 is needed. You can enable prefix suppression on links between R1-R2 and it would work like a charm. But on this question i'd choose A

it's A, modelled in GNS3 , verified. R4#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.2.2.2 0 FULL/ - 00:00:36 10.24.0.2 FastEthernet0/0 R4#show ip route ... 10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks O 10.2.2.2/32 [110/2] via 10.24.0.2, 00:00:15, FastEthernet0/0 O 10.3.3.3/32 [110/12] via 10.24.0.2, 00:00:15, FastEthernet0/0 O 10.1.1.1/32 [110/12] via 10.24.0.2, 00:00:15, FastEthernet0/0 C 10.4.4.4/32 is directly connected, Loopback0 C 10.24.0.0/24 is directly connected, FastEthernet0/0

C is correct and neat solution.

C is correct. The reasoning is simple. Firstly, you're suppressing type 1 and type 2 LSAs only for router R4. If you do it on R1, every router will receive prefix suppression from R1, not just R4. Secondly, it's supposed to be performed under interface configuration, not router configuration. This whitepaper from Cisco displays a great example of how it works https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/213404-open-shortest-path-first-prefix-suppress.html

A is more suitable, since not all IOS versions support the command per interface.

A Definitely . Like nikramor i simulated and c is not working. indeed R1 has a 255 priority and thus it's the DR on the left part. Cheers

C is correct it has a type but will work.

Why Option C is Preferred: Precision: Option C targets the interface directly connected to the segment where reduction is needed, minimizing unnecessary LSA advertisements to R4 without globally affecting the entire OSPF process on R1 or any other router. Control: By applying prefix suppression at the interface level, you maintain finer control over which LSAs are suppressed, avoiding potential issues that could arise from globally suppressing LSAs on all interfaces of R1. Why Not Option A: Broad Impact: Applying prefix suppression globally on R1 (Option A) impacts all connected interfaces and can lead to unintended consequences in OSPF routing within the entire area. Overreach: This broader approach might suppress important routing information that other routers in the OSPF area need, potentially leading to suboptimal routing or even routing issues.

answer is C.

A. Because R1 is the DR, we can configure it on under the router ospf.

A is the best answer as far as the config goes. C will NOT work because if you look closely, after the int gi0/0 command, it is now in "router" config mode and it should be in "interface" config mode.

the question is for LSA 1 , 2 to router 4 i would go for C

Going with A. There are 2 approaches for prefix suppression, global mode configuration and interface mode configuration. The global config (option A) only requires the config shown, interface level suppression would need to be applied on multiple interfaces for the same effect.

I testet it on gns3. It is C.

The corect answer is A. Why? 1) The suppression for each transit subnet is effected by the DR for that link 2) Only advertised transit link prefixes are affected, hence the prefixes to be suppressed is only the 10.0.0.0/24 prefix, because 10.24.0.0/24 prefix is a connected prefix to R4. 3) Simply implementing the prefix suppression on R1, will suppress 10.0.0.0/24 prefix in the FIB of R4 4) If you implement ip ospf prefix suppression on R2, it won't suppress the 10.0.0.0/24 prefix on R4, because it is not the DR for that segment.

If you apply A it will have effect in opposite direction as well