Exam 350-401 topic 1 question 380 discussion

Correct is C The policy must be applied on R1 and we have 2 ways. -Apply outbound area 0 (This will affect others areas in this ABR -Apply inbound area 1 (More accurate) Validate on EVE-NG

A. On R3 ip access-list standard R4_L0 deny host 172.16.1.4 permit any router ospf 200 distribute-list R4_L0 in B. On R1 ip prefix-list INTO-AREA1 seq 5 deny 172.16.1.4/32 ip prefix-list INTO-AREA1 seq 10 permit 0.0.0.0/0 le 32 router ospf 200 area 1 filter-list prefix INTO-AREA1 out C. On R1 ip prefix-list INTO-AREA1 seq 5 deny 172.16.1.4/32 ip prefix-list INTO-AREA1 seq 10 permit 0.0.0.0/0 le 32 router ospf 200 area 1 filter-list prefix INTO-AREA1 in D. On R3 ip prefix-list INTO-AREA1 seq 5 deny 172.16.1.4/32 ip prefix-list INTO-AREA1 seq 10 permit 0.0.0.0/0 le 32 router ospf 200 area 1 filter-list prefix INTO-AREA1 in

B is right,the R1 is an ABR router and when using filter list area 1, stop Advertising the LSA type from backbone to area 1 to OUT side filter-list use for out , but you can use Dsitribute-list on both side.

We can filter using distribute-lists or IP-prefix lists. A is incorrect, we can't filter LSA within the area. B is incorrect, we need to filter routes being advertised to Area 1 (ingress direction) D is also incorrect, we can't filter LSA within the area. Filtering LSAs between areas on an ABR or ASBR is accepted. https://networklessons.com/ospf/ospf-distribute-list-filtering

C is correct

Answer is C. Not sure if this reasoning is valid but. If the filter was applied outbound. Would the OSPF tree on R3 and R1 differ for Area 1? And all intra-area routers have to have the same routing information....

Router(config-router)# area area-id filter-list prefix prefix-list-name in Configures the router to filter interarea routes into the specified area. Router(config-router)# area area-id filter-list prefix prefix-list-name out Configures the router to filter interarea routes out of the specified area. so IN is for the area specified (in this case area 1) and out would be other except Area 1

Answer is C: at first i thought it was B, but the keywords in and out are a bit confusing without proper practice. In the command: ospf area 2 filter-list INTO-AREA1 The option of "in" indicates networks going into the specified area The option of "out" indicates networks coming from the specified area

Simulated the exact lab and found that the answer is C the ABR will filter the subnet by not advertising it to the other routers in area 1. It will keep to itself thou

Correction...meant to say C is the correct answer. R1 (ABR) is filtering the LSA as it goes into area 1.

B is correct. R1 (ABR) is filtering the LSA as it goes into area 1.

R3 should not receive the routes but R1 can receive the routes . To prevent R3 from getting the routes, R1 should filter the routes it nees to pass to R3 which is egress direction. b is correct

this is ABR, pay attention to 172.16.13.0/24 (this netw will be filtered) cisco_R3(config-router)#do s runn | i PL_3 ip prefix-list PL_3 seq 10 deny 172.16.13.0/24 ip prefix-list PL_3 seq 20 permit 0.0.0.0/0 le 32 cisco_R3(config-router)# cisco_R3(config-router)#area 22 filter-list prefix PL_3 ? in Filter networks sent to this area <<<<<<<<<<<<<<<<<<< out Filter networks sent from this area cisco_R3(config-router)#area 22 filter-list prefix PL_3 in cisco_R3(config-router)# cisco_R3(config-router)#do s runn | s ospf ip ospf 1 area 22 router ospf 1 area 22 filter-list prefix PL_3 in passive-interface default no passive-interface Ethernet0/0.10 no passive-interface Ethernet0/0.50 network 0.0.0.0 255.255.255.255 area 0 cisco_R3(config-router)#do s runn int Ethernet0/0.50 interface Ethernet0/0.50 encapsulation dot1Q 50 ip address 10.111.10.1 255.255.255.252 ip ospf 1 area 22 end

in - Filters networks sent TO this area out - Filters network sent FROM this area

C is correct. Prefix-list must be area1 inbound. "area inbound" is different compared with "device inbound".

C is valid, tested in EVE. We are filtering route that are entrying area 1 so we filter in. R1 is ABR

Correct answer b) On R1 ip prefix-list INTO-AREA1 seq 5 deny 172.16.1.4/32 ip prefix-list INTO-AREA1 seq 10 permit 0.0.0.0/0 le 32 router ospf 200 area 1 filter-list prefix INTO-AREA1 out R1 is the ABR.