ISPPlanet NMS Series - Castle Rock SNMPc

Network Discovery

Unless disabled during installation, network discovery is launched when you first run SNMPc (right). In the Workgroup Edition, one "discovery agent" runs on the SNMPc host. This agent uses SNMP to retrieve routing, IP address, and ARP tables from one or more "seed routers". It then tries to contact each addressable device using SNMP and one or more community strings. Devices without SNMP are optionally discovered by ICMP ping.

One seed router and community string are supplied during installation; additional seeds, strings, and other parameters are configured as Discovery Agent properties (left). Most admins will limit discovery scope by adding "Include" networks. If using several communities, expect to receive a flurry of SNMP Authentication Traps. We found SNMPc discovery relatively reliable and quick (e.g., 75 seconds for 3 lightly-populated class C subnets). The only device SNMPc couldn't discover was running (inactive) firewall software which caused it to ignore broadcasts. Unfortunately, there is no user control over discovery timeouts (extended in v5.0.8).

SNMPc can also discover application services running on each device. SMTP, FTP, HTTP, Telnet, and four user-specified ports can be scanned and subsequently monitored. If you're seeking an application-level performance monitor, SNMPc is not for you. But if you're looking for a robust network manager with basic port-level polling, read on.

Progress messages are displayed in SNMPc's event viewer. Discovered nodes are created on hierarchical topology maps, either (re)generated from scratch or augmented incrementally. The top-level "root" map illustrates the connectivity between seed routers and subnets. Subnet maps are populated with one node per physical device. Multi-homed devices appear as one node, no matter how many virtual IPs, physical interfaces, or services they host. Nodes, subnets, connectors, and "go to" icons can be copied, added, or deleted manually, using a toolbar. Navigate by clicking on subnet icons, selecting nodes on a tree-like "selection tool", or using toolbar buttons. Pan/Zoom functions help to navigate very large maps, but can take some getting used to.

Properties can be configured for each map object (below, left) . During layout, SNMPc selects an appropriate icon for each device and sets default intervals and community strings. Monitor attributes like "Has SNMP", "Has Web", and "Has FTP" reflect discovery results. Attributes are largely intuitive, with one truly notable exception: To request ICMP monitoring, set read community to $@$PING$@$ (not described in documentation). One scalar SNMP object can be used for status monitoring by configuring Status Variable, Value, and OK Expression (e.g., ifOperStatus.1 = up). Objects can be organized into Groups, handy when finding objects (below, right) or when initiating actions.