The network topology delivered through maps is the product of a number of discovery technologies. Maps can combine these technologies to provide a clear view of the network topology.
- Layer 3
- Layer 2
- Routing (part of the Routing Protocol Extension module)
Discovery and polling considerations
ENA Auto Discovery is an incremental process - some device details appear immediately, and some are only available after a number of hours (e.g. a number of StormWorks discoveries. By default, StormWorks discovery runs every 2 hours).
As a result, seeing a new device in a map does not mean all of its connectivity is discovered. Similarly, changes in network topology are recognized in maps only after discovery has subsequently run and you have refreshed the current map, or opened a new one.
If you define and enable physical connections, ENA will then create the association between the source and destination devices. This creation also uses the discovery process. There will therefore be a delay between defining a connection and ENA then displaying it on a map.
Discovery vs state
Changes in device state are likely to be more frequent than changes in network topology, and maps reports these changes in almost real-time. Device and link state are derived from data returned from ENA polling devices and handling events. By default, the client refreshes state information every 20 seconds.
IP Peering provides visibility into your WAN links, i.e. leased line, Frame Relay DLCIs, ATM VCCs, using subnet masking. It also reflects any manual IP pairings you may have made in ENA.
Traceroute - Ping State
Traceroute - Ping State technology shows layer 3 connectivity between mapped objects, using information from ENA availability monitoring. By default, ENA performs traceroutes every ten minutes, and pings IP addresses within a route every two minutes.
- ENA can return information on devices, including their status, even when intermediate devices are not under its management.
- ENA does not include to a Traceroute - Ping State map those devices that have an IP address that is administratively down.
- ENA does not support networks where load sharing is implemented.
ENA excludes devices and interfaces that return ping information but are not truly layer 3 objects, e.g. switches that only have a layer 3 management address. However, you can amend these device and interface settings through the topology section of entuity.cfg.
Cisco Discovery Protocol (CDP)
CDP is a proprietary layer 2 protocol, that is primarily used to obtain protocol addresses of neighboring devices and discover the platform of those devices. CDP can also be used to show information about the interfaces your router uses. CDP is media- and protocol-independent, and runs on all Cisco-manufactured equipment including routers, bridges, access servers, and switches. It is also a licensed technology available with some other manufacturer's devices.
ENA uses CDP as a method when maintaining links on maps and identifying trunk ports. ENA gathers CDP from the CDP MIBs, providing a complete and fully accurate layer 2 and layer 3 topology. This relies on:
- devices all being under ENA management.
- CDP being enabled globally and on each interface. Including the detail parameter allows the layer 3 addressing that is configured on the neighbor to be displayed.
- CDP is of compatible versions.
- MIB population is working.
Link Layer Discovery Protocol (LLDP)
The IEEE 802.1AB Link Layer Discovery Protocol (LLDP) provides a solution for the configuration issues caused by expanding LANs. It runs over the data link layer, and specifically defines a standard method for Ethernet network devices to advertise information about themselves to other nodes on the network and store the information they discover. LLDP is available as a technology link type on the ENA maps.
Spanning tree provides a vendor neutral technology for visibility into your network. When correctly implemented, ENA discovers bridge links, switch to switch relationships, through polling the Bridge MIB. Complete spanning tree connectivity relies on a contiguous set of ENA managed devices.
Spanning tree shows trunk connectivity, and also includes uplinks when spanning tree is enabled, i.e. they are 'router on a stick' or layer 3 switch connections - fast ethernet connections which can route between VLANs.
Spanning tree will not show uplinks in other cases, and these are then detected using uplink detection.
This technology can be disabled in entuity.cfg by setting the following:
SynOptics Network Management Protocol (SONMP)
SONMP is also known as the Nortel Discovery Protocol (NDP), a Data Link Layer network protocol for discovery of Nortel (Avaya and Ciena) devices. It is available as a technology link type for the ENA maps.
Physical Address Matching
Physical Address Matching includes connections involving ports with VIP Status of Server link or Uplink.
ENA considers an uplink as trunking on a connection to a single port on a router or layer 3 switch. When the port is on a firewall, load balancer or managed host, the uplink is considered a Server link, unless the device has routing capability.
You can amend the uplink detection algorithm through the topology and vipman sections in entuity.cfg. For example, you can configure ENA to:
- identify device types that should be considered as servers, by default load balancers, firewalls and managed hosts.
- amend the detection algorithm to consider analysis of MAC information.
- amend the maximum number of links for an uplink, by default set to 1.
Topology discovery is done by StormWorks discovery. The original topology and changes to that topology take the time of discovery cycle to appear in the topology. Status is shown much quicker.
For the best performance of this link technology:
- MACs must be gathered from the switches.
- ENA should manage all intermediate devices.
- where trunks are not detected and the router is the only MAC that appears on some of the switch to switch links. In this case, the uplink detection suppresses the links to these ports, because it sees more than one device with ports with a single MAC address on that is the router MAC address.
Routing (part of the Routing Protocol Extension module)
Please see this article for information on the following routing protocols.
Border Gateway Protocol (BGP)
Enhanced Interior Gateway Routing Protocol (EIGRP)
Intermediate System to Intermediate System (IS-IS)
Open Shortest Path First (OSPF)
ENA detects managed hosts through the host resources MIB, and identifies their network connections.
User Defined Connections
If ENA does not discover all connections between devices, e.g. a cable connection between devices, you can define a physical connection. This connection is automatically available within maps to which the source and destination devices are included.
Please see this section for further help and information on user defined connections (manual topology).
ENA detects connections between servers running hypervisors and the appropriate switch/router port on the physical network.
IPv6 ND (part of the IPv6 module)
The IPv6 Neighbor Discovery (ND) protocol facilitates the discovery of neighboring devices. Both regular hosts and routers in an IPv6 environment use the IPv6 ND protocol when exchanging information necessary for proper internetwork operation.
ENA supports IPv6 ND through the IPv6 module, which is activated through configure.
ENA detects virtual machines (VMs) that run on managed hypervisors. ENA also independently manages these VMs as Managed Host or Ping Only devices. ENA maps these virtual machines to their hypervisors through their virtual NIC.