"A" and "D" are already applied, "B" is not required as traffic only needs to be captured and not limited, so "drop" is incorrect. "C" is correct, however it would be enough to set the appropriate source and destination IP pairs, as Aikat and others wrote.
https://community.cisco.com/t5/switching/ospf-dies-when-apply-acl/td-p/794381
This thread suggested to use "permit ospf any any" for simplicity, because of the multicast addressing.
Existing ACL permits R3 to R4 and vise versa to form OSPF neighborship
what we see is that R1 is the one forming the neighborship with both R3 and R4, and for that we either need to monitor source/destinations in the ACL, or simply add ospf any any
The ACL is identifying traffic from R4 to R3 and vice versa, I don't think there is any multihop communication for ospf. ospf traffic is contained to the local segment
(hellos, LSAs, DR/BDR)
With option C:
R1#show policy-map control-plane
Control Plane
Service-policy input: COPP
Class-map: OSPF (match-all)
14 packets, 1316 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: access-group name OSPF
We see packets now. The reason: There are no ospf control plane packets between routers R4 and R3 in the diagram. However when adding option C to the acl we now match control plane packets destined to our router.
if the acl wasnt right then why we have full ospf adj?....i mean we have hellos exhange full/bdr and right ospf process.
if we hasnt full state then the right answer will be the c but i think the copp policy must be configured A
Remember than when the traffic do not match the policy it simply does not apply the policy and the traffic is treated normally. That is why we have full adjacencies between the routers.
this is mcast and in addition look carefully at R1 R2 R3 interface ip addresses
only C can solve it from the listed answers and will catch bot R1<-R2 and R2<->R3
seems like ..... should be C because of the multicast..
I'm not very sure but I vote for C
https://community.cisco.com/t5/routing/access-list-ospf/td-p/781095
The configured policy map must be assigned in the control plan
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/15-0SY/configuration/guide/15_0_sy_swcg/control_plane_policing_copp.pdf
why? i see the COPP is already config?
the first two line of the left picture...
upvoted 2 times
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