How does CA Spectrum model connections?

Document ID : KB000118641
Last Modified Date : 29/10/2018
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Question:
How does CA Spectrum model connections?
Answer:
Spectrum can use a variety of information on the device to create connections, if available on the device.

A. How Spectrum uses SAT to resolve connections:

SAT connections are made from the device forwarding tables.
Under dot1dtp table, there are entries for MAC address and a port that tells you what MAC address this port hears on this device.
The MAC address should correspond to only 1 IF on the other device. These come from the bridge MIB (or q-Bridge MIB).
I checked the dot1dTpFdb table and see if the MIB is missing the MAC address here, so mapping is missed.
dot1dTpFdbEntry 1.3.6.1.2.1.17.4.3.1 as we can see there is no value here.
This can be verified from the sim as the sapwalk app should pull the entire SNMP tree.

B. How Spectrum uses CDP to resolve connections:

1)Both devices must be modeled on the same landscape

2) Spectrum reads the following objects from the ipAddrTable:
        a) ipAdEntAddr (1.3.6.1.2.1.4.20.1.1) 
        b) ipAdEntIfIndex (1.3.6.1.2.1.4.20.1.2)
        c) ipAdEntNetMask (1.3.6.1.2.1.4.20.1.3)
This information is used to populate the deviceIPAddressList and deviceIPMaskList

3) Spectrum reads the CDP Table for the cdpCacheAddress(1.3.6.1.4.1.9.9.23.1.2.1.1.4) on each device, which returns something like: 436281344.10616832

4) If Spectrum can match the cdpCacheAddress with a valid interface/IPAddr from the deviceIPAddressList, then Spectrum will create the connection.

Example:

1.3.6.1.4.1.9.9.23.1.2.1.1.4.436281344.10616832, OctetString , RO , fixed (0xc050d7fc) Device ip. A

1.3.6.1.4.1.9.9.23.1.2.1.1.4.436281344.3473408, OctetString , RO , fixed (0xc0000084) Device ip. B

So if Device ip. A was a valid address on the second device, we should make a connection between these two Interfaces. (defined by If Index 436281344 on both devices in this case).


Note: You may not get a connection to be created with SIMs, because SIMS only change the local IP address, not any remote addresses and if the other address is a SIM address it won't work. 
You can manually modify the IP address (on the SIM though and then get a connection).

In this case I changed Device ip. A to a valid IP on the other device, and a connection was made with the SIMs.
I found a problem related to Cisco Nexus 5500's where they do not provide information from the ipAddrTable therefore Spectrum fails to create the connections.
This is a Cisco problem, and the customer will need to check with Cisco for a solution.