Exam 200-301 topic 1 question 484 discussion

Going with D A is wrong because ip mtu of R14 and R86 are different B is wrong because because ip ospf priority is configured inside router-config, it should be on the interface C is wrong because ip ospf priority is 0 on R14 and it makes R14 not participate on ospf dr/bdr election, the network type is broadcast so i assume dr/bdr should be elected otherwise the network type should be point-to-point D is correct answer - because mtu are same for both routers, participates in dr/bdr election

I'm literally skipping these questions.

B and D literally just different orders on R14 B is ip ospf 10 area 0 ip mtu 1500 router ospf 10 ip ospf priority 255 D is ip ospf priority 255 ip ospf 10 area 0 ip mtu 1500 router ospf 10

Awful question and Cisco shouldn't try to confuse you like this but here's how I'd answer it quickly. Eliminate the mtu mismatch answers. So it's between B and D now. D is correct because it gives r14 a 255 priority. Step 1: find mtu match (B & D) Step 2: find priority 255 for R14. Only D has 255. A- incorrect mtu mismatch B- incorrect priority for R14 C- incorrect priority for R14 D- Correct mtu and priority. Correct me if I'm wrong or have a faster way.

D is correct

Impossible answer, the MTU must match or OSPF will not work.. come on man, this was the first thing covered in my course material on OSPF

Don't u specify the area in the network command?

WTFFFFF. A have a diferente size of MTU! 1400 and 1500. its the 1st for exclude. lol this dump is very dump

going with D, A is clearly wrong due to MTU mismatch For the people that think D is wrong, you need to look at the entire command line, because I got tricked at the beginning as well. It does provide "ip ospf 10 area 0" on both the loopback and actual interface (not just loopback only)

An OSPF priority of 0 does not prevent the router from establishing OSPF adjacencies.

Router with "priority 0" and another with "priority default (1)" formed adjacency and exchanged LSAs and LSDBs normally (I tested it in P.Trace and OSPF dynamic routing works normally), the difference is that there will not be a DR Backup in case fail (that's all). One will be DR Other (neighbor Full/DR) and one DR (neighbor Full/DROther), and BDR appears written that it does not exist, because priority 0 cannot be neither DR nor BDR. (Observation: "point-to-point type" is recommended for this type of connection.) However, the exercise asks them to act as a central point for exchanging information, in this case "it gives the impression" that he asked us to select a "DR". Letter "D" would be the most correct because using "ip ospf priority 255" (in the interface) we define R14 as DR.

Tested in packet tracer. A. OSPF neighborship was established even with mismatched MTU. B. You cannot enter this command on R14: router ospf 10 - ip ospf priority 255 C. OSPF neighborship was established R14 will be FULL/DROTHER, R86 will be DR so it cannot be the central point for exchanging OSPF information between routers D. OSPF neighborship was established

C is for me. A is mtu issue B is network issue D is network issue

as per the standard OSPF specification defined in RFC 2328, “OSPF Version 2”. Specifically the RFC states the following: 10.6 - Database Description Packet. If the Interface MTU field in the Database Description packet indicates an IP datagram size that is larger than the router can accept on the receiving interface without fragmentation, the Database Description packet is rejected. Basically this means that if a router tries to negotiate an adjacency on an interface in which the remote neighbor has a larger MTU, the adjacency will be denied. The idea behind this check is two-fold. The first is to alleviate a problem in the data plane, in which a sending host transmits packets to a receiver that are too large to accept. Typically, Path MTU Discovery (PMTUD) should be implemented on the sender to prevent this case, however this process relies on ICMP messages that could possibly be filtered out in the transit path due to a security policy. The second, and most important issue, is to alleviate a problem in the control plane in which OSPF packets are exchanged.

It's absolutely D

option A would be best if MTU match... option D has no routes advertised...

D is wrong because the network cmd is not configured for the networks. How can you form neighbours without it