Spectrum can use a variety of information, if they're available, on the device to create connections.
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 interface (IF) on the other device. These come from the bridge MIB (or q-Bridge MIB).
If the dot1dTpFdb table MIB table is missing the MAC address, then mapping is missed. If the dot1dTpFdbEntry (188.8.131.52.184.108.40.206.3.1) table is missing, then there will be no value available to map the interface to.
In Spectrum, connections are resolved for SAT by checking for dot1dTpFdbAddress, dot1dTpFdbPort, dot1dTpFdbStatus and dot1dBasePortIfIndex:
- dot1dTpFdbAddress – Neighbor Device MAC Address list -> Instance
- dot1dTpFdbPort - Neighbor Device Port list
- dot1dTpFdbStatus - Neighbor Port Status list
- dot1dBasePortIfIndex – Local & Neighbor device port mapping list
Neighbor device port MAC Address is obtained from the dot1dTpFdbAddress table. Neighbor port MAC Address to Local port IfIndex mapper value is learned from the dot1dTpFdbPort table.
Once the Local port IfIndex mapper value is learned (dot1dTpFdbPort). Spectrum reads the dot1dBasePortIfIndex table to map local & neighbor device ports. (This step will be processed for each entry in the table)
a) ipAdEntAddr (220.127.116.11.18.104.22.168.1.1)
B. How Spectrum uses CDP to resolve connections:
1. Both devices must be modelled on the same landscape
2. Spectrum reads the following objects from the ipAddrTable:
b) ipAdEntIfIndex (22.214.171.124.126.96.36.199.1.2)
c) ipAdEntNetMask (188.8.131.52.184.108.40.206.1.3)
This information is used to populate the deviceIPAddressList and deviceIPMaskList
3. Spectrum reads the CDP Table for the cdpCacheAddress(220.127.116.11.18.104.22.168.22.214.171.124.1.4) on each device, which returns an index number. For example, 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.
126.96.36.199.188.8.131.52.184.108.40.206.1.4.436281344.10616832, OctetString , RO , fixed (0xc050d7fc) Device ip. A
220.127.116.11.18.104.22.168.22.214.171.124.1.4.436281344.3473408, 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 see a connection 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 you can change Device ip. A to a valid IP on the other device, and a connection should be made with the SIMs.