Consider the scenario shown in the figure (Figure 2-a) below. A router R1 aggreg
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Question
Consider the scenario shown in the figure (Figure 2-a) below. A router R1 aggregates the subnets 160.16.0.0/24 labelled [a] and 160.16.1.0/24 labelled [b] into the general prefix address 160.16.0.0/23 [ab]. Router R1 announces this general prefix [ab] to router R2 which in turn transmits it to router R3 and R4. Due to the rule of split horizon this general prefix is not readvertised back to R2 by R3 or R4 but it is exchanged between each other (R3 and R4) as shown in the figure.) Consider the scenario shown in the figure (Figure 2-a) below. A router R1 aggregates the subnets 160.16.0.0/24 labelled [a] and 160.16.1.0/24 labelled [b] into the general prefix address 160.16.0.0/23 [ab]. Router R1 announces this general prefix [ab] to router R2 which in turn transmits it to router R3 and R4. Due to the rule of split horizon this general prefix is not readvertised back to R2 by R3 or R4 but it is exchanged between each other (R3 and R4) as shown in the figure.
At a later stage, the component prefix [b] of the general prefix [ab] is unreachable and R1 is forced to announce just the remaining single route to subnet [a] to R2 which forwards the same to R3 and R4 (refer to figure 2-b). Assume, the update message from R2 to R3 gets lost and R3 still keeps the information of the reachable general prefix [ab] received via R2 at an earlier time. Furthermore, R3 continues to exchange the general prefix [ab] with R4 which now does not have a valid route to the failed part of the general prefix. Explain in some detail what problem/s might surface if R4 accepts the general prefix [ab] from R3.
R3 R1 ab R2 160.16.0.0/24a ab 160.16.1.0/24b a b R4 Figure2-:aExplanation / Answer
# As we kanow in the (Figure-2a) a and b are able to route in whole network without creating loop with the help of spilit horizon and due to the rule of spilit horizon this general prifix is not advertised back to R2 by R3 or R4 but it is exchanged between each other.
#In the (Figure-2b) b is in block state and a is routed in whole route R3 and R4 is unable to readvertise it's path due to loop problem and further path is block.Between R2 and R3 the path is block so the readvertisement isn't take place due to the unavailability of path. the various packet should have been dropped due to the inconsistent route to send packets further.R4 accepts because according to the first scenerio R3 qand R4 are unable to readvertise it's path.