For an OSPF neighbor relationship to form, several parameters on adjacent interfaces must match. On Broadcast and NBMA network types, OSPF requires that the primary IP addresses of the two interfaces belong to the same subnet, which means their subnet masks must be identical. The scenario states the interfaces are on different network segments with different masks, which violates this rule.

However, the Point-to-Point (P2P) and Point-to-Multipoint (P2MP) network types do not perform this subnet mask check. By changing the network type to either P2P or P2MP, the routers will ignore the mask mismatch and can successfully establish a neighbor relationship, assuming other parameters like Area ID and timers match.

B. NBMA: This network type requires interfaces to be on the same subnet with identical masks to form an adjacency, which is not the case in this scenario.

D. Broadcast: Similar to NBMA, the Broadcast network type enforces a strict check requiring identical subnet masks for neighbor adjacency, which is violated here.

1. Huawei HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Training Material.

Reference: Page 101

Section "OSPF Neighbor Relationship Establishment".

Quote/Content: The material lists the conditions for establishing a neighbor relationship. It explicitly states: "The subnet masks of the interfaces must be the same. (This is not checked on P2P and P2MP interfaces.)" This directly confirms that both P2P and P2MP network types bypass the subnet mask check.

2. RFC 2328 - OSPF Version 2.

Reference: Section 10.5

"Receiving Hello Packets".

Quote/Content: This section details the processing of received Hello packets. It specifies that for broadcast and NBMA interfaces

"The Network Mask in the received Hello Packet should be the same as the Network Mask of the receiving interface." It also explicitly states

"On point-to-point networks... the Network Mask in the Hello Packet is not checked." Point-to-Multipoint networks are treated as a collection of point-to-point links and inherit this behavior.