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NNM Discovery

Jayashree Arunkumar

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Initial IP Discovery

1. ovstart starts ovspmd2. ovspmd starts netmon3. netmon queries NNM management station’s SNMP

agent for configuration information which includes– IP Address– Subnet mask– Default route– ARP Cache

4. For each IP Address found– Ping it to make sure it is alive– Make an SNMP query to determine SNMP version

supported– Use SNMP to retrieve configuration information

5. Repeat step 4 until no new IP addresses are found

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netmon Polling of a new node

1. If node responds to ping, netmon places it in the database

2. Configuration poll uses SNMP to gather all node information

3. Topology poll on connector device determines which nodes are heard from which ports (sysObjID – oid_to_type file)

4. Discovery poll retrieves the ARP cache to find more nodes

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Setting Object Attributes and Symbol type

Configuration poll gathers direct information including nodes sysobjectID

Derives other attributes from sysobjectID– Correlates system object ID to symbol type and

other miscellaneous attributes in oid_to_sym file– Correlates system object ID to topology and

vendor attributes in oid_to_type or HPoid2type files

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Initial IPX Discovery

Routing Information Protocol (RIP) – finds the networks

Diagnostic Broadcast – finds netware systems on networks

Diagnostic Request – obtains system information and status

Service Advertising Protocol (SAP) Request – gets information about server names

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MAC Layer Discovery and Monitoring

MAC layer discovery and monitoring– Bridge MIB (RFC 1493)– Repeater MIB (RFC 2108)– 8023MAU MIB (RFC 1515)

MAC interface status determination Unnumbered interfaces (Routers)

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Discovery of HTTP nodes

System object ID obtained Port 80 polled for Home Page

isHTTPSupported Web Server Home Page Port 280 Polled for Configuration Page

isHTTPManaged Web Server Configuration Page

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Extended Topology Discovery

Heterogeneous Layer 2 switched network management (LAN & WAN)

Targeted views for quickly identifying root cause– View switched environment and complex

relationships between devices– View network services such as OSPF and VLAN

Enhances NNM views: neighbor, station, internet

Superior root-cause analysis via improved path detection

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What extended topology discovers

“Layer-two” connectivity VLAN information ATM information OSPF information

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Troubleshooting IP Discovery

Common problems which affect IP discovery– Incorrect subnet mask– Non-matching SNMP community name– Non-SNMP routers– Too few SNMP nodes– Insufficient or isolated traffic– Bridged, not routed, networks– Name Resolution (DNS) problems

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Name Resolution problems

Opening ovw takes a long time Labels appear as IP addresses instead of

hostnames– use checkDNS.ovpl –v (NNMCD\support) to check

DNS performance If DNS request takes a long time, netmon

generates an alert Timeout can be controlled by –T option in

netmon.lrf file

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Tracing and Logging Operations

Logging – records externally observable events such as connection establishment, state changes and errors

Tracing – captures inbound and outbound packets going through the network

netmon –M <tracemask> (2 – ICMP, 8 – SNMP) to enable tracing

netmon –a <action-nr> sends an event to netmon to dump its internal data structures

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Configuring Extended Discovery

You can change how netmon discovers your network by:– telling netmon to discover more by

managing nodes– giving netmon a seed file to speed up initial

discovery– specifying options in netmon.lrf

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Using loadhosts

Few SNMP nodes / restrict management to specific nodes

Place nodes directly into the topology database

loadhosts –m <subnetmask> filename For controlled discovery turn off new

node discovery polling process

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Seeding Initial IP Discovery

By default, netmon only discovers nodes on the local subnet only

A seed file is a simple ASCII file containing a list of IP addresses, preferably gateways and routers

All networks connected to the seed file entries are discovered exclusively

Seed file typically contains– IP address of management station– IP address of default router– IP address in other networks ( routers, file servers etc.)

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Using a seed file

1. Create a seed file, using routers and gateways

2. Modify the netmon.lrf file Add –s <pathname/filename> to the options eg: -s “C\:/dir/seedfile”

3. Use ovaddobj on netmon’s LRF cd %OV_LRF% ovaddobj netmon.lrf

4. Stop netmon

5. Redo initial discovery, if required

6. Restart netmon

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Redo Initial Discovery

Stop NNM Remove Openview databases

– cd %OV_DB%– remove \install_dir\databases\openview

Remove all events– remove \install_dir\databases\eventdb

Re-register fields– ovstart ovwdb– ovw -fields

Start NNM

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Useful netmon Discovery options

-J Speed up discovery -r Query the routing table -Q SNMP-queue-length -S Discover secondary addresses -w Control discovery of software

loopback addresses

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Discovery filters

Collection domain – set of nodes actively discovered and monitored by NM

Purpose of discovery filter– Limit netmon’s discovery and polling– Reduce IP devices actively monitored– Limit objects added to the topology database– Reduce computer resources overhead– Reduce polling cycle time

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Configuring netmon.noDiscover

Newly discovered IP addresses are compared against the file

If the IP address is in the file, it is ignored – No discovery is done on that address

Valid entries are– 10.36.104.*– 10.225.50-100.*– 10.2.197.1

Must be created in \install_dir\conf\ folder

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Discovery Filter Evaluation

Network and Segment objects are created after discovery filtering

If a node passes, all interfaces associated with that node also pass

If an interface passes, the node associated with the interface passes, including all other interfaces

If you want to filter a node completely, you must filter the node object and all the interfaces associated with that node

filter file– \install_dir\conf\C\filters

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Example Discovery Filter

Filters {

CMCLan “CMC Local LAN devices”

{ “IP Address” ~ 192.168.44.* }

}

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Applying a Discovery Filter

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netmon.noDiscover vs Discovery Filter

Discovery filter queries a node and then evaluates whether the node should be included in the database

netmon.noDiscover does not even query the device if IP address matches – saves network bandwidth and speeds up discovery

For certain types of devices (routers, switches etc.) the only option is to use Discovery filter