Key Concepts 939 Device SizingWith the exception of the sizing stage (explained below), each of thestages runs sequentially, and the sequence is repeated for each subnetthat is being discovered. The sizing stage runs once only, when all theother stages have been executed for all of the subnets being discovered.The purpose of each stage is described below:IP PingIn order to detect which IP nodes exist, this stage performs an IP Ping overthe specified ranges of addresses for the subnet. If no ranges arespecified, a default range is deduced from the subnet address and subnetmask of the subnet being discovered. This range excludes the subnetaddress itself (lowest address value) and the subnet broadcast address(highest address value).Device Capability DetectionThis stage is applied to each device that responded to a ping in theprevious stage. Its purpose is to determine if a device supports certainnetwork protocols. Specifically, these are:■ SNMP■ HTTP■ TelnetThe most detailed information is generally obtained from devices thatsupport SNMP. For these devices 3Com Network Director initially startsthe communication using the read community string as originallyspecified in the Network Discovery wizard. Having successfullycommunicated using the read community string it then attemptscommunication using the write community string(s), again obtained fromthe Network Discovery wizard. While the write community string is notheavily used by the discovery process (except a small part of topology), itis used extensively by other features of 3Com Network Director.Consequently, if the write community cannot be successfully determined,discovery will continue, but add a warning to the report provided at theend of discovery.3Com Network Director detects HTTP and Telnet capabilities byattempting to open a TCP connection to the device using ports 80 and 23respectively. The purpose of this detection is to decide whether to enable
