Why isn't discovery finding all my nodes?

SNMPc's auto-discovery is an heuristic algorithm and will probably not discover all your devices, nor even the same devices when run twice. That said, it should at least find a few. It uses several methods to find IP addresses. It starts with the seeds you give it and polls the routing tables and ARP address caches to find out what the device is talking to. It then does broadcasts and tries to ping ranges of addresses depending on what it's found. You can also always add icons manually to the map using the Insert/Map Object menu. When you insert a device, make sure you enter the IP address in the General tab and set poll interval and get/set community names in the attributes tab. Some devices need to be configured with the managers address for security reasons.

Discovery is configured through the Config/Discovery agents menu item. The main switch to turn it on and off is the "Enable Discovery" checkbox. You can then turn on and off the different methods used. Make sure both the subnet broadcasts and ping scans are checked for optimal results. You can disable polling on this screen by unchecking the boxes in the "Polling Config" section.

The next tab - proto - allows you to set up automatic polling for different services and also to create icons for devices that do not have SNMP to poll with pings.

Seeds are a starting place for discovery. Usually you would supply the addresses of some routers with SNMP since they would know about other routers and devices communicating through them. The comm tab allows you to set the community name used to poll for SNMP information and to set up multiple community names. Finally filters allows you to limit the reach of discovery so it doesn't get out and start discovering devices over the internet. You can also use this if you have multiple polling agents to specify what networks each agent is responsible for. Discovery will try to lay out the devices based on their IP address and subnet mask, placing devices with multiple IP addresses (routers) at the top level.

However, most people will not use the maps that autodiscovery creates. They will let discovery find most of thier stuff, add the things that wern't discovered by hand, then rearrange the maps into a more phyiscal representation of their network.


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