Two days ago I posted the follwing question from the MS\nTrng Kit for 70-216. I received several responses but none\nthat really explained why the answer to the question was\nselection 'd.'\n\nSo, I lined out in binary form all of the eight IP\naddresses. It turns out that the 'd' answer that changes\nthe subnet mask to 0/21 isolates the right most 3 bits of\nthe 3rd octet.\n\nWith the 0/21 mask there are two nets using 24 and 30 in\nthe second octet. Then the host addresses are changed by\none in the third octet.\n\nBut, the question remains, why does this make the routing\ntables simpler for the router?\n\nInteresting problem, don't you love that MS does not give\nan explanation.\n\n"You are the new administrator of a 2000 node network.\nThere is only one router on the entire network, which\nprovides all the computers with Internet access. The\ncompany's ISP has assigned the following 8 network\naddresses to them:\n\n10.24.32.0/24\n10.24.33.0/24\n10.24.34.0/24\n10.30.35.0/24\n10.30.36.0/24\n10.30.37.0/24\n10.30.38.0/24\n10.30.39.9/24\n\nWhat subnet mask could you use to minimize the complexity\nof the routing tables while maintaining the existing\nInternet connectivity?\n\na. 255.255.252.0\nb. 255.255.255.252\nc. 255.255.255.248\nd. 255.255.248.0 "