unexpected connection created from discovery
Article ID: 220628
Updated On:
Products
Issue/Introduction
unexpected connection created on discovery. Autodiscovery log in debug mode shows the following created connection:
Jul 16 03:32:33 ADISC debug started.
Current state: Auto Discovery finished.
Jul 16 03:34:53 Discovery queue after queuing new work:
Jul 16 03:34:53 Discovery queue length=1:
Jul 16 03:34:53 Device Model Handle 0x4033def, DISCOVER_CONNECTIVITY( 0x25e0022 )
Jul 16 03:34:53
Jul 16 03:34:53 Start processing queued discovery: Device Model Handle 0x4033def, DISCOVER_CONNECTIVITY( 0x25e0022 )
Jul 16 03:34:53 Auto Discovery started.
Jul 16 03:34:53 Discover connections Models List : 0x4033def,
AutoDiscovery Mapping options:
Create WA_Link: No
Create LAN : No
Create Fanout: No
Create Phys_Addr: No
Run ATM Discovery: No
Read IP Addr Tables: Yes
Create Pingable Access Points for WLC: NoReconfigure interfaces: No
Read IP Route Table: No
Read ARP Tables: Yes
Read DP Tables: Yes
Read SAT Tables: Yes
Read Spanning Trees: Yes
Traffic Resolution: Yes
Jul 16 03:34:53 collecting Layer-2 device connectivity information.
Discovering connections for model: -- device NOR2-MDFA1-XXX/0x4033def (GnSNMPDev)
......
Device NOR2-MDFA1-XXX/0x4033def (GnSNMPDev) has 4 MAC addresses:
1: 0:13:c6:2:62:9b --> Port NOR2-MDFA-XXX_eth0(ifType=6) ,
2: 0:13:c6:2:62:9c --> Port NOR2-MDFA1-XXX_eth1(ifType=6) ,
3: 0:e:8e:70:ae:a7 --> Port NOR2-MDFA1-XXX_wlan0(ifType=6) ,
4: 92:1d:c6:b0:93:67 --> Port NOR2-MDFA1-XXX_wwan1(ifType=6) ,
Jul 16 03:34:53 start collecting LACP protocol data on device NOR2-MDFA1-XXX/0x4033def
....
Connection created ( ( IP): Port NOR2-MDFA1-XXX_wwan0(ifType=1) <--> Port SEA2-MDFA1-XXX_wwan0(ifType=1)
Jul 16 03:34:54 Port NOR2-MDFA1-XXX_eth0(ifType=6) (ifIndex=2, subnet type=) 1002d) routes to 1 subnets: ((10.254.156.72,255.255.255.
Jul 16 03:34:54 processing Layer-2 connectivity information.
Jul 16 03:34:54 start processing SATon device NOR2-MDFA1-XXX/0x4033def
Jul 16 03:34:54 end of SAT data process on device NOR2-MDFA1-XXX0x4033def
# of devices to map: 1
Jul 16 03:34:54 collecting Layer-2 neighbor device connectivity information.
Environment
Release : 10.4.1,21.2.x
Component : Spectrum Core / SpectroSERVER
Resolution
At Layer 2 DISCOVERY it uses
Source Address Tables (SAT)
Cisco DISCOVERY PROTOCOL (CDP)
Link Layer Discovery Protocol (LLDP)
At Layer 3 DISCOVERY it uses:
IP Address Table
IP Route Table
The IP Address Table works as follows:
Description:
By default, Spectrum uses ipAddrTable to resolve the L3 layer connections (Router/Brouter/L3 Switch/etc.). The IP Address Table contains information about interfaces such as configured IP address, subnet mask and ifIndex. Spectrum then identifies the neighbor device and the port based on the subnet address of local interface. This subnet address is calculated by a combination of the IP address and the subnet mask.
For example:
Local interface IP = 10.208.235.242, Subnet mask = 255.255.255.248 (28)
Subnet Address = 10.208.235.240
Subnet Range = 10.208.235.241 - 10.208.235.246
To create a connection, the neighbor interface should be under the same subnet range and should be already modeled in Spectrum.
In the example given above, the IP address of the neighbor interface will be one of 10.208.235.241 - 10.208.235.246 (excluding 10.208.235.242, which is the local interface IP). Spectrum then tries to reach each IP from this subnet range. If only one such IP is found to be reachable and that interface is found to be modeled in Spectrum then the connection will be resolved.
In case there are multiple IP addresses reachable in that subnet range then, the connections will not be created because neighbor interface cannot be uniquely identified.
From the https://techdocs.broadcom.com/us/en/ca-enterprise-software/it-operations-management/dx-netops/21-2/Fault-Monitoring-with-DX-Spectrum/managing-network/modeling-and-managing-your-it-infrastructure/discovering-and-modeling-your-network/how-to-discover-and-model-the-network.html
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