[0] 0.48.122.168.in-addr.arpa.: domain name does not exist [3600] 1.48.122.168.in-addr.arpa. domain name pointer comm595-0203net-gw.bu.edu [0] 2.48.122.168.in-addr.arpa.: domain name does not exist [0] 3.48.122.168.in-addr.arpa.: domain name does not exist [0] 4.48.122.168.in-addr.arpa.: domain name does not exist [0] 5.48.122.168.in-addr.arpa.: domain name does not exist [0] 6.48.122.168.in-addr.arpa.: domain name does not exist [0] 7.48.122.168.in-addr.arpa.: domain name does not exist [0] 8.48.122.168.in-addr.arpa.: domain name does not exist [0] 9.48.122.168.in-addr.arpa.: domain name does not exist [0] 10.48.122.168.in-addr.arpa.: domain name does not exist [3600] 11.48.122.168.in-addr.arpa. domain name pointer comm595-210aer01.bu.edu [3600] 12.48.122.168.in-addr.arpa. domain name pointer comm595-211aer01.bu.edu [3600] 13.48.122.168.in-addr.arpa. domain name pointer comm595-222aer01.bu.edu [0] 14.48.122.168.in-addr.arpa.: domain name does not exist [0] 15.48.122.168.in-addr.arpa.: domain name does not exist [0] 16.48.122.168.in-addr.arpa.: domain name does not exist [0] 17.48.122.168.in-addr.arpa.: domain name does not exist [0] 18.48.122.168.in-addr.arpa.: domain name does not exist [0] 19.48.122.168.in-addr.arpa.: domain name does not exist [0] 20.48.122.168.in-addr.arpa.: domain name does not exist [0] 21.48.122.168.in-addr.arpa.: domain name does not exist [0] 22.48.122.168.in-addr.arpa.: domain name does not exist [0] 23.48.122.168.in-addr.arpa.: domain name does not exist [0] 24.48.122.168.in-addr.arpa.: domain name does not exist [0] 25.48.122.168.in-addr.arpa.: domain name does not exist [0] 26.48.122.168.in-addr.arpa.: domain name does not exist [0] 27.48.122.168.in-addr.arpa.: domain name does not exist [0] 28.48.122.168.in-addr.arpa.: domain name does not exist [0] 29.48.122.168.in-addr.arpa.: domain name does not exist [0] 30.48.122.168.in-addr.arpa.: domain name does not exist [3600] 31.48.122.168.in-addr.arpa. domain name pointer comm595-0203-031.bu.edu [3600] 32.48.122.168.in-addr.arpa. domain name pointer comm595-0203-032.bu.edu [3600] 33.48.122.168.in-addr.arpa. domain name pointer comm595-0203-033.bu.edu [3600] 34.48.122.168.in-addr.arpa. domain name pointer comm595-0203-034.bu.edu [3600] 35.48.122.168.in-addr.arpa. domain name pointer comm595-0203-035.bu.edu [3600] 36.48.122.168.in-addr.arpa. domain name pointer comm595-0203-036.bu.edu [3600] 37.48.122.168.in-addr.arpa. domain name pointer comm595-0203-037.bu.edu [3600] 38.48.122.168.in-addr.arpa. domain name pointer comm595-0203-038.bu.edu [3600] 39.48.122.168.in-addr.arpa. domain name pointer comm595-0203-039.bu.edu [3600] 40.48.122.168.in-addr.arpa. domain name pointer comm595-0203-040.bu.edu [3600] 41.48.122.168.in-addr.arpa. domain name pointer comm595-0203-041.bu.edu [3600] 42.48.122.168.in-addr.arpa. domain name pointer comm595-0203-042.bu.edu [3600] 43.48.122.168.in-addr.arpa. domain name pointer comm595-0203-043.bu.edu [3600] 44.48.122.168.in-addr.arpa. domain name pointer comm595-0203-044.bu.edu [3600] 45.48.122.168.in-addr.arpa. domain name pointer comm595-0203-045.bu.edu [3600] 46.48.122.168.in-addr.arpa. domain name pointer comm595-0203-046.bu.edu [3600] 47.48.122.168.in-addr.arpa. domain name pointer comm595-0203-047.bu.edu [3600] 48.48.122.168.in-addr.arpa. domain name pointer comm595-0203-048.bu.edu [3600] 49.48.122.168.in-addr.arpa. domain name pointer comm595-0203-049.bu.edu [3600] 50.48.122.168.in-addr.arpa. domain name pointer comm595-0203-050.bu.edu [3600] 51.48.122.168.in-addr.arpa. domain name pointer comm595-0203-051.bu.edu [3600] 52.48.122.168.in-addr.arpa. domain name pointer comm595-0203-052.bu.edu [3600] 53.48.122.168.in-addr.arpa. domain name pointer comm595-0203-053.bu.edu [3600] 54.48.122.168.in-addr.arpa. domain name pointer comm595-0203-054.bu.edu [3600] 55.48.122.168.in-addr.arpa. domain name pointer comm595-0203-055.bu.edu [3600] 56.48.122.168.in-addr.arpa. domain name pointer comm595-0203-056.bu.edu [3600] 57.48.122.168.in-addr.arpa. domain name pointer comm595-0203-057.bu.edu [3600] 58.48.122.168.in-addr.arpa. domain name pointer comm595-0203-058.bu.edu [3600] 59.48.122.168.in-addr.arpa. domain name pointer comm595-0203-059.bu.edu [3600] 60.48.122.168.in-addr.arpa. domain name pointer comm595-0203-060.bu.edu [3600] 61.48.122.168.in-addr.arpa. domain name pointer comm595-0203-061.bu.edu [3600] 62.48.122.168.in-addr.arpa. domain name pointer comm595-0203-062.bu.edu [3600] 63.48.122.168.in-addr.arpa. domain name pointer comm595-0203-063.bu.edu [3600] 64.48.122.168.in-addr.arpa. domain name pointer comm595-0203-064.bu.edu [3600] 65.48.122.168.in-addr.arpa. domain name pointer comm595-0203-065.bu.edu [3600] 66.48.122.168.in-addr.arpa. domain name pointer comm595-0203-066.bu.edu [3600] 67.48.122.168.in-addr.arpa. domain name pointer comm595-0203-067.bu.edu [3600] 68.48.122.168.in-addr.arpa. domain name pointer comm595-0203-068.bu.edu [3600] 69.48.122.168.in-addr.arpa. domain name pointer comm595-0203-069.bu.edu [3600] 70.48.122.168.in-addr.arpa. domain name pointer comm595-0203-070.bu.edu [3600] 71.48.122.168.in-addr.arpa. domain name pointer comm595-0203-071.bu.edu [3600] 72.48.122.168.in-addr.arpa. domain name pointer comm595-0203-072.bu.edu [3600] 73.48.122.168.in-addr.arpa. domain name pointer comm595-0203-073.bu.edu [3600] 74.48.122.168.in-addr.arpa. domain name pointer comm595-0203-074.bu.edu [3600] 75.48.122.168.in-addr.arpa. domain name pointer comm595-0203-075.bu.edu [3600] 76.48.122.168.in-addr.arpa. domain name pointer comm595-0203-076.bu.edu [3600] 77.48.122.168.in-addr.arpa. domain name pointer comm595-0203-077.bu.edu [3600] 78.48.122.168.in-addr.arpa. domain name pointer comm595-0203-078.bu.edu [3600] 79.48.122.168.in-addr.arpa. domain name pointer comm595-0203-079.bu.edu [3600] 80.48.122.168.in-addr.arpa. domain name pointer comm595-0203-080.bu.edu [3600] 81.48.122.168.in-addr.arpa. domain name pointer comm595-0203-081.bu.edu [3600] 82.48.122.168.in-addr.arpa. domain name pointer comm595-0203-082.bu.edu [3600] 83.48.122.168.in-addr.arpa. domain name pointer comm595-0203-083.bu.edu [3600] 84.48.122.168.in-addr.arpa. domain name pointer comm595-0203-084.bu.edu [3600] 85.48.122.168.in-addr.arpa. domain name pointer comm595-0203-085.bu.edu [3600] 86.48.122.168.in-addr.arpa. domain name pointer comm595-0203-086.bu.edu [3600] 87.48.122.168.in-addr.arpa. domain name pointer comm595-0203-087.bu.edu [3600] 88.48.122.168.in-addr.arpa. domain name pointer comm595-0203-088.bu.edu [3600] 89.48.122.168.in-addr.arpa. domain name pointer comm595-0203-089.bu.edu [3600] 90.48.122.168.in-addr.arpa. domain name pointer comm595-0203-090.bu.edu [3600] 91.48.122.168.in-addr.arpa. domain name pointer comm595-0203-091.bu.edu [3600] 92.48.122.168.in-addr.arpa. domain name pointer comm595-0203-092.bu.edu [3600] 93.48.122.168.in-addr.arpa. domain name pointer comm595-0203-093.bu.edu [3600] 94.48.122.168.in-addr.arpa. domain name pointer comm595-0203-094.bu.edu [3600] 95.48.122.168.in-addr.arpa. domain name pointer comm595-0203-095.bu.edu [3600] 96.48.122.168.in-addr.arpa. domain name pointer comm595-0203-096.bu.edu [3600] 97.48.122.168.in-addr.arpa. domain name pointer comm595-0203-097.bu.edu [3600] 98.48.122.168.in-addr.arpa. domain name pointer comm595-0203-098.bu.edu [3600] 99.48.122.168.in-addr.arpa. domain name pointer comm595-0203-099.bu.edu [3600] 100.48.122.168.in-addr.arpa. domain name pointer comm595-0203-100.bu.edu [3600] 101.48.122.168.in-addr.arpa. domain name pointer comm595-0203-101.bu.edu [3600] 102.48.122.168.in-addr.arpa. domain name pointer comm595-0203-102.bu.edu [3600] 103.48.122.168.in-addr.arpa. domain name pointer comm595-0203-103.bu.edu [3600] 104.48.122.168.in-addr.arpa. domain name pointer comm595-0203-104.bu.edu [3600] 105.48.122.168.in-addr.arpa. domain name pointer comm595-0203-105.bu.edu [3600] 106.48.122.168.in-addr.arpa. domain name pointer comm595-0203-106.bu.edu [3600] 107.48.122.168.in-addr.arpa. domain name pointer comm595-0203-107.bu.edu [3600] 108.48.122.168.in-addr.arpa. domain name pointer comm595-0203-108.bu.edu [3600] 109.48.122.168.in-addr.arpa. domain name pointer comm595-0203-109.bu.edu [3600] 110.48.122.168.in-addr.arpa. domain name pointer comm595-0203-110.bu.edu [3600] 111.48.122.168.in-addr.arpa. domain name pointer comm595-0203-111.bu.edu [3600] 112.48.122.168.in-addr.arpa. domain name pointer comm595-0203-112.bu.edu [3600] 113.48.122.168.in-addr.arpa. domain name pointer comm595-0203-113.bu.edu [3600] 114.48.122.168.in-addr.arpa. domain name pointer comm595-0203-114.bu.edu [3600] 115.48.122.168.in-addr.arpa. domain name pointer comm595-0203-115.bu.edu [3600] 116.48.122.168.in-addr.arpa. domain name pointer comm595-0203-116.bu.edu [3600] 117.48.122.168.in-addr.arpa. domain name pointer comm595-0203-117.bu.edu [3600] 118.48.122.168.in-addr.arpa. domain name pointer comm595-0203-118.bu.edu [3600] 119.48.122.168.in-addr.arpa. domain name pointer comm595-0203-119.bu.edu [3600] 120.48.122.168.in-addr.arpa. domain name pointer comm595-0203-120.bu.edu [3600] 121.48.122.168.in-addr.arpa. domain name pointer comm595-0203-121.bu.edu [3600] 122.48.122.168.in-addr.arpa. domain name pointer comm595-0203-122.bu.edu [3600] 123.48.122.168.in-addr.arpa. domain name pointer comm595-0203-123.bu.edu [3600] 124.48.122.168.in-addr.arpa. domain name pointer comm595-0203-124.bu.edu [3600] 125.48.122.168.in-addr.arpa. domain name pointer comm595-0203-125.bu.edu [3600] 126.48.122.168.in-addr.arpa. domain name pointer comm595-0203-126.bu.edu [3600] 127.48.122.168.in-addr.arpa. domain name pointer comm595-0203-127.bu.edu [3600] 128.48.122.168.in-addr.arpa. domain name pointer comm595-0203-128.bu.edu [3600] 129.48.122.168.in-addr.arpa. domain name pointer comm595-0203-129.bu.edu [3600] 130.48.122.168.in-addr.arpa. domain name pointer comm595-0203-130.bu.edu [3600] 131.48.122.168.in-addr.arpa. domain name pointer comm595-0203-131.bu.edu [3600] 132.48.122.168.in-addr.arpa. domain name pointer comm595-0203-132.bu.edu [3600] 133.48.122.168.in-addr.arpa. domain name pointer comm595-0203-133.bu.edu [3600] 134.48.122.168.in-addr.arpa. domain name pointer comm595-0203-134.bu.edu [3600] 135.48.122.168.in-addr.arpa. domain name pointer comm595-0203-135.bu.edu [3600] 136.48.122.168.in-addr.arpa. domain name pointer comm595-0203-136.bu.edu [3600] 137.48.122.168.in-addr.arpa. domain name pointer comm595-0203-137.bu.edu [3600] 138.48.122.168.in-addr.arpa. domain name pointer comm595-0203-138.bu.edu [3600] 139.48.122.168.in-addr.arpa. domain name pointer comm595-0203-139.bu.edu [3600] 140.48.122.168.in-addr.arpa. domain name pointer comm595-0203-140.bu.edu [3600] 141.48.122.168.in-addr.arpa. domain name pointer comm595-0203-141.bu.edu [3600] 142.48.122.168.in-addr.arpa. domain name pointer comm595-0203-142.bu.edu [3600] 143.48.122.168.in-addr.arpa. domain name pointer comm595-0203-143.bu.edu [3600] 144.48.122.168.in-addr.arpa. domain name pointer comm595-0203-144.bu.edu [3600] 145.48.122.168.in-addr.arpa. domain name pointer comm595-0203-145.bu.edu [3600] 146.48.122.168.in-addr.arpa. domain name pointer comm595-0203-146.bu.edu [3600] 147.48.122.168.in-addr.arpa. domain name pointer comm595-0203-147.bu.edu [3600] 148.48.122.168.in-addr.arpa. domain name pointer comm595-0203-148.bu.edu [3600] 149.48.122.168.in-addr.arpa. domain name pointer comm595-0203-149.bu.edu [3600] 150.48.122.168.in-addr.arpa. domain name pointer comm595-0203-150.bu.edu [3600] 151.48.122.168.in-addr.arpa. domain name pointer comm595-0203-151.bu.edu [3600] 152.48.122.168.in-addr.arpa. domain name pointer comm595-0203-152.bu.edu [3600] 153.48.122.168.in-addr.arpa. domain name pointer comm595-0203-153.bu.edu [3600] 154.48.122.168.in-addr.arpa. domain name pointer comm595-0203-154.bu.edu [3600] 155.48.122.168.in-addr.arpa. domain name pointer comm595-0203-155.bu.edu [3600] 156.48.122.168.in-addr.arpa. domain name pointer comm595-0203-156.bu.edu [3600] 157.48.122.168.in-addr.arpa. domain name pointer comm595-0203-157.bu.edu [3600] 158.48.122.168.in-addr.arpa. domain name pointer comm595-0203-158.bu.edu [3600] 159.48.122.168.in-addr.arpa. domain name pointer comm595-0203-159.bu.edu [3600] 160.48.122.168.in-addr.arpa. domain name pointer comm595-0203-160.bu.edu [3600] 161.48.122.168.in-addr.arpa. domain name pointer comm595-0203-161.bu.edu [3600] 162.48.122.168.in-addr.arpa. domain name pointer comm595-0203-162.bu.edu [3600] 163.48.122.168.in-addr.arpa. domain name pointer comm595-0203-163.bu.edu [3600] 164.48.122.168.in-addr.arpa. domain name pointer comm595-0203-164.bu.edu [3600] 165.48.122.168.in-addr.arpa. domain name pointer comm595-0203-165.bu.edu [3600] 166.48.122.168.in-addr.arpa. domain name pointer comm595-0203-166.bu.edu [3600] 167.48.122.168.in-addr.arpa. domain name pointer comm595-0203-167.bu.edu [3600] 168.48.122.168.in-addr.arpa. domain name pointer comm595-0203-168.bu.edu [3600] 169.48.122.168.in-addr.arpa. domain name pointer comm595-0203-169.bu.edu [3600] 170.48.122.168.in-addr.arpa. domain name pointer comm595-0203-170.bu.edu [3600] 171.48.122.168.in-addr.arpa. domain name pointer comm595-0203-171.bu.edu [3600] 172.48.122.168.in-addr.arpa. domain name pointer comm595-0203-172.bu.edu [3600] 173.48.122.168.in-addr.arpa. domain name pointer comm595-0203-173.bu.edu [3600] 174.48.122.168.in-addr.arpa. domain name pointer comm595-0203-174.bu.edu [3600] 175.48.122.168.in-addr.arpa. domain name pointer comm595-0203-175.bu.edu [3600] 176.48.122.168.in-addr.arpa. domain name pointer comm595-0203-176.bu.edu [3600] 177.48.122.168.in-addr.arpa. domain name pointer comm595-0203-177.bu.edu [3600] 178.48.122.168.in-addr.arpa. domain name pointer comm595-0203-178.bu.edu [3600] 179.48.122.168.in-addr.arpa. domain name pointer comm595-0203-179.bu.edu [3600] 180.48.122.168.in-addr.arpa. domain name pointer comm595-0203-180.bu.edu [3600] 181.48.122.168.in-addr.arpa. domain name pointer comm595-0203-181.bu.edu [3600] 182.48.122.168.in-addr.arpa. domain name pointer comm595-0203-182.bu.edu [3600] 183.48.122.168.in-addr.arpa. domain name pointer comm595-0203-183.bu.edu [3600] 184.48.122.168.in-addr.arpa. domain name pointer comm595-0203-184.bu.edu [3600] 185.48.122.168.in-addr.arpa. domain name pointer comm595-0203-185.bu.edu [3600] 186.48.122.168.in-addr.arpa. domain name pointer comm595-0203-186.bu.edu [3600] 187.48.122.168.in-addr.arpa. domain name pointer comm595-0203-187.bu.edu [3600] 188.48.122.168.in-addr.arpa. domain name pointer comm595-0203-188.bu.edu [3600] 189.48.122.168.in-addr.arpa. domain name pointer comm595-0203-189.bu.edu [3600] 190.48.122.168.in-addr.arpa. domain name pointer comm595-0203-190.bu.edu [3600] 191.48.122.168.in-addr.arpa. domain name pointer comm595-0203-191.bu.edu [3600] 192.48.122.168.in-addr.arpa. domain name pointer comm595-0203-192.bu.edu [3600] 193.48.122.168.in-addr.arpa. domain name pointer comm595-0203-193.bu.edu [3600] 194.48.122.168.in-addr.arpa. domain name pointer comm595-0203-194.bu.edu [3600] 195.48.122.168.in-addr.arpa. domain name pointer comm595-0203-195.bu.edu [3600] 196.48.122.168.in-addr.arpa. domain name pointer comm595-0203-196.bu.edu [3600] 197.48.122.168.in-addr.arpa. domain name pointer comm595-0203-197.bu.edu [3600] 198.48.122.168.in-addr.arpa. domain name pointer comm595-0203-198.bu.edu [3600] 199.48.122.168.in-addr.arpa. domain name pointer comm595-0203-199.bu.edu [3600] 200.48.122.168.in-addr.arpa. domain name pointer comm595-0203-200.bu.edu [3600] 201.48.122.168.in-addr.arpa. domain name pointer comm595-0203-201.bu.edu [3600] 202.48.122.168.in-addr.arpa. domain name pointer comm595-0203-202.bu.edu [3600] 203.48.122.168.in-addr.arpa. domain name pointer comm595-0203-203.bu.edu [3600] 204.48.122.168.in-addr.arpa. domain name pointer comm595-0203-204.bu.edu [3600] 205.48.122.168.in-addr.arpa. domain name pointer comm595-0203-205.bu.edu [3600] 206.48.122.168.in-addr.arpa. domain name pointer comm595-0203-206.bu.edu [3600] 207.48.122.168.in-addr.arpa. domain name pointer comm595-0203-207.bu.edu [3600] 208.48.122.168.in-addr.arpa. domain name pointer comm595-0203-208.bu.edu [3600] 209.48.122.168.in-addr.arpa. domain name pointer comm595-0203-209.bu.edu [3600] 210.48.122.168.in-addr.arpa. domain name pointer comm595-0203-210.bu.edu [3600] 211.48.122.168.in-addr.arpa. domain name pointer comm595-0203-211.bu.edu [3600] 212.48.122.168.in-addr.arpa. domain name pointer comm595-0203-212.bu.edu [3600] 213.48.122.168.in-addr.arpa. domain name pointer comm595-0203-213.bu.edu [3600] 214.48.122.168.in-addr.arpa. domain name pointer comm595-0203-214.bu.edu [3600] 215.48.122.168.in-addr.arpa. domain name pointer comm595-0203-215.bu.edu [3600] 216.48.122.168.in-addr.arpa. domain name pointer comm595-0203-216.bu.edu [3600] 217.48.122.168.in-addr.arpa. domain name pointer comm595-0203-217.bu.edu [3600] 218.48.122.168.in-addr.arpa. domain name pointer comm595-0203-218.bu.edu [3600] 219.48.122.168.in-addr.arpa. domain name pointer comm595-0203-219.bu.edu [3600] 220.48.122.168.in-addr.arpa. domain name pointer comm595-0203-220.bu.edu [3600] 221.48.122.168.in-addr.arpa. domain name pointer comm595-0203-221.bu.edu [3600] 222.48.122.168.in-addr.arpa. domain name pointer comm595-0203-222.bu.edu [3600] 223.48.122.168.in-addr.arpa. domain name pointer comm595-0203-223.bu.edu [3600] 224.48.122.168.in-addr.arpa. domain name pointer comm595-0203-224.bu.edu [3600] 225.48.122.168.in-addr.arpa. domain name pointer comm595-0203-225.bu.edu [3600] 226.48.122.168.in-addr.arpa. domain name pointer comm595-0203-226.bu.edu [3600] 227.48.122.168.in-addr.arpa. domain name pointer comm595-0203-227.bu.edu [3600] 228.48.122.168.in-addr.arpa. domain name pointer comm595-0203-228.bu.edu [3600] 229.48.122.168.in-addr.arpa. domain name pointer comm595-0203-229.bu.edu [3600] 230.48.122.168.in-addr.arpa. domain name pointer comm595-0203-230.bu.edu [3600] 231.48.122.168.in-addr.arpa. domain name pointer comm595-0203-231.bu.edu [3600] 232.48.122.168.in-addr.arpa. domain name pointer comm595-0203-232.bu.edu [3600] 233.48.122.168.in-addr.arpa. domain name pointer comm595-0203-233.bu.edu [3600] 234.48.122.168.in-addr.arpa. domain name pointer comm595-0203-234.bu.edu [3600] 235.48.122.168.in-addr.arpa. domain name pointer comm595-0203-235.bu.edu [3600] 236.48.122.168.in-addr.arpa. domain name pointer comm595-0203-236.bu.edu [3600] 237.48.122.168.in-addr.arpa. domain name pointer comm595-0203-237.bu.edu [3600] 238.48.122.168.in-addr.arpa. domain name pointer comm595-0203-238.bu.edu [3600] 239.48.122.168.in-addr.arpa. domain name pointer comm595-0203-239.bu.edu [3600] 240.48.122.168.in-addr.arpa. domain name pointer comm595-0203-240.bu.edu [3600] 241.48.122.168.in-addr.arpa. domain name pointer smgpodium222.bu.edu [3600] 242.48.122.168.in-addr.arpa. domain name pointer smgpodium211.bu.edu [3600] 243.48.122.168.in-addr.arpa. domain name pointer smgpodium210.bu.edu [0] 244.48.122.168.in-addr.arpa.: domain name does not exist [0] 245.48.122.168.in-addr.arpa.: domain name does not exist [0] 246.48.122.168.in-addr.arpa.: domain name does not exist [0] 247.48.122.168.in-addr.arpa.: domain name does not exist [0] 248.48.122.168.in-addr.arpa.: domain name does not exist [0] 249.48.122.168.in-addr.arpa.: domain name does not exist [0] 250.48.122.168.in-addr.arpa.: domain name does not exist [0] 251.48.122.168.in-addr.arpa.: domain name does not exist [0] 252.48.122.168.in-addr.arpa.: domain name does not exist [0] 253.48.122.168.in-addr.arpa.: domain name does not exist [0] 254.48.122.168.in-addr.arpa.: domain name does not exist [0] 255.48.122.168.in-addr.arpa.: domain name does not exist