Brocade Communications Systems IP250 user manual 53-1003056-01

IP discovery overview 3

2.Discovery queries the database to retrieve the IP address for each previously discovered device and adds these IP addresses to the list of candidate IP addresses.

3.Discovery adds the IP addresses from the IP address file to the list of candidate addresses.

4.As the discovery cycle proceeds, discovery adds addresses from the ping sweep address ranges to the list of candidate addresses.

5.Discovery searches for neighbors of a discovered device using the information located in the device's SNMP Link Layer Discovery Protocol (LLDP), Foundry Discovery Protocol (FDP), Cisco Discovery Protocol (CDP), and Address Resolution Protocol (ARP) tables. To search for neighbors, you must configure discovery to search for neighbor addresses (refer to “Configuring advanced discovery profile preferences” on page 78).

After creating the list of candidate IP addresses, discovery uses multiple threads to probe devices. You can define how many threads can be used at one time. Threads operate in parallel, so communication to multiple devices occurs simultaneously. Each thread takes one address from the list of candidate IP addresses and probes it. The first step in probing is to determine whether the device is reachable or not. Discovery provides two methods to determine reachability. The first method uses ICMP ping to probe the device. The second method opens a connection to the IP address (currently to the Telnet port). This serves as a "ping" to confirm that the IP address is reachable and some device is listening. By default, if the device responds by either accepting or rejecting the connection, then the connection is closed and discovery continues.

The next step uses SNMP queries. The first query determines whether the device is a IronWare OS or Network OS device or not. Discovery rotates through a list of candidate SNMP community strings until it finds one that works. For devices that already exist in the database, the community string recorded in the database for that device is tried first.

If you configure discovery to search for neighbor addresses (refer to “Configuring advanced discovery profile preferences” on page 78), the second query scans the device's SNMP ARP table. Discovery adds any IP address from the ARP table to the list of candidate IP addresses.

Similarly, if you configure discovery to search for neighbor addresses (refer to “Configuring advanced discovery profile preferences” on page 78), the third query scans the device’s SNMP LLDP, FDP, and CDP tables. Any neighbor IP address is added to the list of candidate IP addresses to probe. Discovery adds any IP address from the LLDP, FDP, and CDP tables to the list of candidate IP addresses.

Discovery also tries to determine the host name of the device by requesting the Management application server operating system to perform various mappings of the device IP addresses to host names and host names back to IP addresses, using whatever mechanism the operating system uses (typically Domain Name Server) to determine the host name for a device.

If discovery determines that the device is reachable and manageable, then discovery uses the full set of SNMP queries to collect asset information from the device. Discovery then adds or updates the device in the database and sends notification to other applications.

Rediscovery updates can occur using any of the following methods:

•Lazy polling.

•Adaptive discovery (triggered by snmp traps).

•Manual rediscovery (refer to “IP Rediscovery” on page 108).

Brocade Network Advisor IP User Manual	33
53-1003056-01