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-:a