In the exhibit, R2 receives the same OSPF update from both R1 and R3. OSPF has mechanisms to prevent unnecessary processing of duplicate LSAs (Link-State Advertisements).
Step-by-Step Breakdown:
OSPF LSA Processing:
OSPF uses LSAs to exchange link-state information between routers. When a router receives an LSA, it checks if it already has a copy of the LSA in its Link-State Database (LSDB).
Duplicate LSAs:
If R2 has already received and processed the update from R1, it will ignore the update from R3 because it already has the same LSA in its database. OSPF uses the concept of flooding, but it does not reprocess LSAs that it already knows about.
R2 Behavior:
R2 will keep the update from R1 (the first one it received) and will ignore the same LSA from R3, as it is already in the LSDB.
Juniper
Reference: OSPF LSA Processing: Junos adheres to OSPF standards, ensuring that duplicate LSAs are not processed multiple times to avoid unnecessary recalculations.

IBGP (Internal Border Gateway Protocol) is used to exchange routing information between routers within the same AS (Autonomous System).
Step-by-Step Breakdown:
TTL of 255:
By default, IBGP sessions are established with a TTL (Time to Live) value of 255. This allows IBGP neighbors to communicate over multiple hops within the AS without requiring any additional configuration.
Full Mesh Requirement:
IBGP requires a logical full mesh between all IBGP routers to ensure that routing information is fully distributed within the AS. Since IBGP does not propagate routes learned from one IBGP peer to another by default, a full mesh topology is needed unless route reflectors or BGP confederations are used.
Juniper
Reference: IBGP Full Mesh: Juniper recommends using route reflectors in large networks to simplify IBGP full-mesh requirements.