HP OpenView System Administration Handbook [Electronic resources] : Network Node Manager, Customer Views, Service Information Portal, HP OpenView Operations نسخه متنی

Chapter 5. Network Discovery

The default behavior of NNM is to stop the discovery of the network at the first router relative to the discovery station (my IP address + my subnet mask). To prevent discovery of the entire Internet, NNM will not discover beyond the first router it encounters. Early implementations of network management tools had no limitations and would wreak havoc on the entire networked community. One important thing to remember when performing initial discovery is that it is extremely network-bandwidth intensive. Initial discovery is not something you should do during peak network traffic hours. The NNM station performs a ping of all the devices in the arp cache of the router followed by a series of snmpgets until all the devices listed in the router's arp cache are discovered. To list a device's arp cache you can execute the following snmpwalk command, providing the hostname or IP address of the device.

snmpwalk

hostname

at

This command traverses the

a ddress

t ranslation (

at ) branch of the Mib-II subtree, otherwise known as the arp cache. By using this command, you can get an idea of how much the discovery of this router will impact your network. Use

grep [1] and

wc to obtain the exact count of interfaces in the arp cache. The output of the following command will be a number indicating the number of entries in the arp cache of the specified hostname:

[1] To perform these commands on a Windows system, you will need UNIX tools such as cygwin. Cygwin is a UNIX environment, developed by Red Hat for Windows.

snmpwalk

hostname

at | grep atNetAddr | wc l

One of the requirements for Sealey Inc. includes the capability of the network management application to discover remote networks. Local network monitoring is not required. Only customer networks need to be monitored. The application needs to automatically discover specified portions of the network. Because the customer networks are constantly changing, they also need the ability to manually add devices as necessary. On occasion, they might need to exclude devices from discovery to minimize the number of managed nodes discovered.

Many customers have private community names for security purposes. The application required by Sealey Inc. will need to provide access to SNMP devices configured with private community names. Another security issue is the use of firewalls. Sealey Inc. will need to determine how to handle access to customer devices through firewalls.

Because network discovery and monitoring can be network bandwidth intensive, Sealey Inc. wants to be able to actively monitor the performance of its network monitoring solution. The company may need additional resources to handle all its customers.