Router R3 receives an LSA with the sequence number 111 from router R4 and then receives another copy of the LSA with a sequence number 112 from router R2. What does router R3 do with the LSA from R2?
A.
R3 discards the LSA received from R2 and sends a copy of the LSA from its link state base to R2.
B.
R3 installs the LSA received from R2 in its link state database and floods a copy to its neighbors.
C.
R3 discards the LSA received from R2 and sends an ACK to R2.
D.
R3 installs the LSA received from R2 in its link state database, sends an ACK to R2, and floods a copy to its neighbors.
D. R3 installs the LSA received from R2 in its link state database, sends an ACK to R2, and floods a copy to its neighbors.
Explanation:
This question refers to OSPF's Link-State Advertisement (LSA) handling based on sequence numbers.
Here's what happens:
Router R3 receives an LSA with sequence number 111 from R4.
Later, it receives the same LSA but with a higher sequence number (112) from R2.
Since 112 > 111, it means the LSA from R2 is more recent than the one currently in R3’s link-state database.
According to OSPF protocol behavior:
Install the newer LSA (seq 112) in its link-state database (LSDB).
Send an acknowledgment (LSAck) to R2 for the LSA.
Flood the new LSA to its other neighbors (except the one it received it from).
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jbmac
1 week ago