Your SNMP-based management system discovers failed routers, physical interfaces and circuits. But, if you're running an IP network, what about snafus in the control plane that are not so easy to detect? These include logical (rather than physical) hiccups that could be impacting your network, and you might not even be aware of it.

So says at least two start-ups determined to help IP network managers quickly troubleshoot Layer 3 problems. Packet Design and Ipsum Networks have separately developed products in a new category generically known as "route analytics."

Shipping as appliances that are router-like in nature but only "listen" to route-exchange information (they do not forward packets), the devices help network managers gain ongoing visibility into the actual Layer 3 paths that packets are taking across IP networks at any point in time. These include large networks with multiple domains.

Finding the root cause of IP routing faults involves tapping into the routing protocols in use, such as Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS). By harnessing the reachability information shared among routers via these Layer 3 routing protocols, Packet Design and Ipsum say they can help network operators quickly pinpoint router misconfigurations, route flaps (intermittent route changes that can degrade performance) and other Layer 3 problems.

Packet Design executive vice president of marketing Jeff Raice, for example, pointed to one company (now a beta customer) that discovered the hard way that the dual edge routers and access circuits in place for redundancy weren't configured properly for hot failover. When the primary circuit was cut, the organization experienced an outage, despite the backup resources. SNMP polling, notes Raice, would indicate the backup network elements to be healthy in this situation, while Layer 3 troubleshooting would have spotted this misconfiguration before the crisis.

Both companies' products are router vendor-independent. Next time: A bit more detail on form factors, protocol support and pricing.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Jim Metzler is vice president of Ashton, Metzler & Associates.