AS4643 203.13.136.0/21 CIDR and IP Range Summary.ASN: 4643 - Optus Customer NetworkHost Count: 2046Addressable IPs: 2048203.13.136.0/24203.13.137.0/24203.13.138.0/24203.13.139.0/24203.13.140.0/24203.13.141.0/24203.13.142.0/24203.13.143.0/24