You can use any of the following Classic Discovery methods to discover your network:
Starts at the gateway address (the address of the nearest router to the computer running Discovery) for the current subnet and uses the ARP (Address Resolution Protocol) Cache of that device to determine information about the devices. The ARP Cache contains the IP-to-MAC (physical network) address mappings.
Discovery retrieves the gateway address from the computer on which it is running and gets the IP list from the ARP Cache on that router. It then discovers the subnets nearest that router and for each subnet it discovers, queries its gateway, doing the same thing over and over again.
For each device found in the ARP Cache, an SNMP request is initiated. If the device does not respond, it is assumed to be a non‑SNMP device, just the IP address is retrieved, and the object is created as an Unclassified_TCP object.
Pings all of the devices on the network based on the subnet mask, finds IP devices, and then retrieves SNMP information. If no SNMP information is retrieved, just the IP address is retrieved, and the object is created as an Unclassified_TCP device. This is the slowest but most thorough method.
Similar to ARP Cache, Fast ARP saves time by checking only the ARP Cache of routers. Fast ARP is the best method for updating the MDB when you do not want to use the more intensive searches provided by Ping Sweep and ARP Cache. This is the fastest way to discover your network.
Limits the discovery of devices to those that are defined in the domain name server (DNS). The IP address of each of these devices is combined with the defined subnet mask to determine whether or not to discover the device. (In contrast, the Ping Sweep option tries to discover all active devices numerically, without regard to their definition in the DNS).
Each Discovery method has advantages and disadvantages. The Ping Sweep method provides more comprehensive quantitative information—in the form of the number of devices—because every device on the network is pinged. Even devices not recognized by the router, which may not be discovered through the ARP Cache method, can be discovered using Ping Sweep.
On the other hand, ARP Cache provides the MAC and IP address information on all the devices that are found in the ARP Cache of the router. Ping Sweep, however, generates additional network traffic and is thus more time consuming than ARP Cache and Fast ARP. Sometimes, to discover every device in the network, a combination of Ping Sweep and ARP Cache is required.
We recommend that when you first install your product that you run a Ping Sweep Discovery so that a comprehensive search of your network is done. Periodically, it is a good idea to run an ARP Cache Discovery to check your network for devices added after the initial Discovery was done.
|
Copyright © 2010 CA.
All rights reserved.
|
|