An Inbound filter list on R3 and R7 would prevent the route from being installed in Area 0, the criteria were to make sure it did not reach Area 2 and 3 only. An outbound filter can be applied on ABR's, so I believe A is the answer.
I completely agree. An inbound filter on R3 and R7 would prevent the route from entering Area 0, but since the goal is to stop it from reaching Area 2 and 3. So A is Correct
WRONG.
distribute-list out command. This command only works on the routes being redistributed by Autonomous system boundary Router into OSPF
https://community.cisco.com/t5/networking-knowledge-base/distribute-list-out-command-in-ospf/ta-p/3120931
The correct answer it´s "C"
What does that command have to do with the question? You apply a filter list using the "filter-list prefix" command, where prefix is a previously defined rule that blocks the network we don't want to reach Area 2 and 3. The outbound filter list applied on R3 and R7 would stop advertising LSA3 out of all it’s other connected areas (including area 0). So it would work.
No, outbound direction is NOT correct.
CISCOs definition of that command is:
Router(config-router)# area <area-id> filter-list prefix <prefix-list-name> in
>> Configures the router to filter interarea routes INTO the specified area.
You are arguing with device direction view you know from ACLs, but filter-lists have area direction views, which are different. So INBOUND direction is correct.
R1(config-router)#area 0 filter-list prefix checkDirection ?
in Filter networks sent to this area
out Filter networks sent from this area
So what are you saying when you can filter outbound?
You are NOT correct!
Outbound for filter lists is not correct.
FIlter-lists are related to areas, not devices.
So.. area 2 and area 3 from view of R3 unf R7 is INBOUND!
The correct answer it´s "C"
Tested this in eve-ng.
=== ON R7=====
ip prefix-list BLOCK seq 5 deny 6.6.6.6/32
ip prefix-list BLOCK seq 10 permit 0.0.0.0/0 le 32
router ospf 1
area 2 filter-list prefix BLOCK in
=== ON R3=====
ip prefix-list BLOCK seq 5 deny 6.6.6.6/32
ip prefix-list BLOCK seq 10 permit 0.0.0.0/0 le 32
router ospf 1
area 3 filter-list prefix BLOCK in
ip prefix-list FILTER-6.6.6.6 seq 5 deny 6.6.6.6/32
ip prefix-list FILTER-6.6.6.6 seq 10 permit 0.0.0.0/0 le 32
area 2 filter-list prefix FILTER-6.6.6.6 in (FILTER MY ROUTE AS IT ENTERS AREA 2)
R9#show ip route 6.6.6.6
% Network not in table
The answer is C.
Q: prevent the R6 loopback from getting INTO Area 2 and Area 3 FROM Area 0 - keywords are INTO (Area 2 and 3) & FROM (area 0) here.
R3 and R7 are able to filter routes (LSAs) outbound as they leave Area 1. Or inbound as they enter Area 2 & 3.
An outbound filter-list on R3 and R7 filters the LSA outbound for area 1 and IN to area 0. An inbound filter-list on R3 and R7 filters the LSA inbound for area 0 and IN to area 2 and 3
see figure 9-24 OSPF Area Filtering Topology in the OCG
The question states: "R6 loopback from getting into Area 2 and Area 3 from Area 0".
this alone tells me that the starting point is Area 0, having said this filter-lists direction is from the perspective of the area.
So from Area 0 to Area 2/3 that is definitely OUTBOUND.
I see peeps referring to distribute-lists and Area2/3 as starting point - question does not say that!
OSPF Route Filtering
Inbound Filtering: When you apply a filter list inbound on a router, you prevent specific routes from being accepted into the routing table from a specific neighbor or area. This means the routes will not be learned by that router from its neighbors.
Outbound Filtering: When you apply a filter list outbound on a router, you prevent specific routes from being advertised to specific neighbors or areas. This means the routes will not be sent out from that router to its neighbors.
Correct answer is C.
Tested it on GNS3 you need to look from the perspective of the are that the LSA will be propagated, in that case R3 and R7 will take the prefix 6.6.6.6/32 and "put" it in are 2 and 3, which means that you need to filter this prefix from entering the area.
like this:
ip prefix-list OSPF seq 10 deny 6.6.6.6/32
ip prefix-list OSPF seq 20 permit 0.0.0.0/0 le 32
router ospf 1
area 3 filter-list prefix OSPF in
A is the correct answer, Outbound from Area 0 into Area 1 and 2 will be prevented but it will appear in Area 0 and not in Area 1 and 2. Guess this answers the question
https://www.youtube.com/watch?v=PUNo0VHzHzI
Outbound will also prevent routers in area 0 to learn LSA type 3
Inbound will prevent only the targeted area to learn that LSA type 3.
!
ip prefix-list FILTER_R6_Lo0 deny 6.6.6.6/32
ip prefix-list FILTER_R6_Lo0 permit 0.0.0.0/0 le 32
!
router ospf 1
area 2 filter-list prefix FILTER_R6_Lo0 in
area 3 filter-list prefix FILTER_R6_Lo0 in
!
I meant C is the best answer.
Outbound will also prevent routers in area 0 to learn LSA type 3
Inbound will prevent only the targeted area to learn that LSA type 3.
!
ip prefix-list FILTER_R6_Lo0 deny 6.6.6.6/32
ip prefix-list FILTER_R6_Lo0 permit 0.0.0.0/0 le 32
!
router ospf 1
area 2 filter-list prefix FILTER_R6_Lo0 in
area 3 filter-list prefix FILTER_R6_Lo0 in
!
So A is the best answer.
From Cisco training source:
To configure Type-3 LSA filtering, use the area area-number filter-list prefix prefix-list-name in | out command under OSPF configuration mode. The referenced prefix list is used to match the subnets and masks to be filtered. The area-number and the in | out option of the area filter-list command work together, as follows:
When out is configured, IOS filters prefixes coming out of the configured area.
When in is configured, IOS filters prefixes going into the configured area.
A voting comment increases the vote count for the chosen answer by one.
Upvoting a comment with a selected answer will also increase the vote count towards that answer by one.
So if you see a comment that you already agree with, you can upvote it instead of posting a new comment.
siteoforigin
Highly Voted 2 years, 5 months ago[Removed]
3 months, 2 weeks agoRREVECO
2 years, 5 months agoCiscoTerminator
4 months, 3 weeks agoH_al
2 years, 4 months agojjeans
2 years, 3 months agoCiscoTerminator
4 months, 3 weeks agojjeans
2 years, 3 months agoAmoako
Highly Voted 2 years, 4 months agomatass_md
Most Recent 2 days, 12 hours agochmacnp
1 month, 1 week agoa67c04a
3 months, 3 weeks agoCiscoTerminator
4 months, 3 weeks agoRfvaz
6 months, 2 weeks ago05b11e1
7 months, 1 week agocy111
8 months, 2 weeks ago[Removed]
9 months agoSwiz005
10 months, 3 weeks agokivi_bg
1 year agoElstak_Dennis
1 year, 2 months agoAblovi
1 year, 3 months agoAblovi
1 year, 3 months agoAblovi
1 year, 3 months agoAblovi
1 year, 3 months agoblueblue2
1 year, 5 months ago